Clinical Bacteriology Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

What are 2 serologic tests that are specific for treponemal infections?

A

Fluorescent treponemal antibody–absorbed (FTA-ABS) test and Treponema pallidum particle agglutination (TPPA) assay

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What stain is used to visualize Chlamydiae, and what characteristic finding would be seen?

A

Giemsa or fluorescent antibody stain; cytoplasmic inclusions (reticulate bodies)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

A colleague tells you that your next patient has confirmed tetanus toxin in his system. What symptoms do you expect this patient to exhibit?

A

Spastic paralysis, risus sardonicus (open grin and raised eyebrows), trismus (lockjaw), and opisthotonos (spinal extensor spasms)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What tests are used to screen for and confirm a case of secondary syphilis?

A

Screen: VDRL/RPR; confirm: FTA-ABS (or dark-field microscopy)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

In a patient with peptic ulcers caused by Helicobacter pylori, how are the bacteria able to thrive in the stomach’s acidic mucosa?

A

Helicobacter pylori is urease ⊕ and can produce ammonia, thus creating an alkaline environment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the laboratory characteristics of Pseudomonas aeruginosa?

A

Aerobic, motile, catalase ⊕, oxidase ⊕, gram ⊖ rod with a grape-like odor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How is Yersinia enterocolitica typically transferred to humans?

A

Pet feces (eg, from puppies), contaminated milk, or pork

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What similarities are there in laboratory characteristics and pathogenicity of Salmonella and Shigella?

A

Both are gram ⊖ rods, oxidase ⊖, non-lactose fermenters, and can invade the GI tract by way of M cells of Peyer patches

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Among lactose nonfermenters, which gram ⊖ bacilli are oxidase negative?

A

Shigella, Salmonella, Proteus, and Yersinia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

A man has watery, nonbloody diarrhea after eating reheated rice 9 hours earlier. Explain how the causative organisms likely survived heating.

A

This is likely a Bacillus cereus infection; spores survive cooking; rewarming the rice promotes spore germination and enterotoxin formation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the modes of transmission of Neisseria meningitidis?

A

Respiratory and oral secretions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What virulence factor is produced by Haemophilus influenzae?

A

Immunoglobulin A (IgA) protease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How sensitive to novobiocin is Staphylococcus saprophyticus?

A

It is novobiocin resistant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

A culture is growing a nonlactose-fermenting, gram ⊖ rod that is commonly associated with wound infection in burn victims. Name the bacteria.

A

Pseudomonas aeruginosa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

A urine culture from a 20-year-old sexually active woman is growing a catalase ⊕ organism. Diagnosis?

A

Staphylococcus saprophyticus (common cause of urinary tract infections in sexually active women)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Which spirochete can be visualized on light microscopy using aniline dyes (Wright or Giemsa stain)?

A

Borrelia (Borrelia is Big); due to size, this is the only spirochete visible on light microscopy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

A 75-year-old smoker has mild flu-like symptoms. Labs show hyponatremia. The antigen of the causative bacteria is detected in the urine. Treatment?

A

Macrolides or quinolones; diagnosis: likely Pontiac fever caused by Legionella pneumophila

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the duration of onset and resolution of food poisoning symptoms from food contaminated with Clostridium perfringens spores?

A

Symptoms occur within 10-12 hours and resolve in 24 hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

A young woman presents with nonpainful, gray vaginal discharge. You suspect Gardnerella. What outcome do you expect on an amine whiff test?

A

A strong fishy odor; mixing the discharge with 10% potassium hydroxide (KOH) solution in an amine whiff test for G vaginalis enhances its odor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

A child is infected with gram ⊕ rods with metachromatic granules and a positive Elek test. How is this infection transmitted?

A

Corynebacterium diphtheriae is transmitted via respiratory droplets

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What lab methods are used to diagnose a chlamydial infection?

A

Nucleic acid amplification tests, such as PCR and visualization on Giemsa or fluorescent antibody-stained smear

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Name 2 polymyxin antibiotics that can be used to treat Pseudomonas aeruginosa infection.

A

Polymyxin B, colistin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

You find oxidase ⊖, gram ⊖, lactose-nonfermenting bacilli. Which agar can be used to differentiate bacteria based on H2S production?

A

Triple sugar iron (TSI) agar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How do Salmonella and Shigella compare with regard to the production of H2S gas?

A

Salmonella spp. (including Salmonella typhi) produce H2S; Shigella do not

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is the vector and the pathogen causing Rocky Mountain spotted fever?

A

Dermacentor (dog tick); bites transmit Rickettsia rickettsii

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What 2 techniques are used to visualize Treponema?

A

Dark-field microscopy or direct fluorescent antibody (DFA) microscopy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

A shepherd presents with hemoptysis. A chest x-ray shows mediastinal widening. Diagnosis?

A

Bacillus anthracis infection (also called woolsorter’s disease; mediastinal widening is due to mediastinitis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

A patient is diagnosed with bacterial vaginosis secondary to Gardnerella vaginalis. What do you expect to see on wet prep?

A

Clue cells with stippled outer margins (vaginal epithelial cells covered with bacteria)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How does Listeria monocytogenes infection commonly present in a healthy individual?

A

As mild, self-limited gastroenteritis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What kind of infection occurs after initial exposure to Mycobacterium tuberculosis?

A

Primary tuberculosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Describe the vaccine used against Haemophilus influenzae.

A

The vaccine consists of a type b capsular polysaccharide (polyribosylribitol phosphate) conjugated to diphtheria toxoid or another protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

One patient has an Actinomyces infection; another has a Nocardia infection. How do you treat each patient?

A

Sulfonamides can treat Nocardia; Actinomyces is treated with Penicillin (Treatment is a SNAP)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Name an aerobic, gram ⊕, acid-fast branching filament.

A

Nocardia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What is the most common serotype of enterohemorrhagic Escherichia coli (EHEC) in the US?

A

O157:H7

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is the mechanism of action of Staphylococcus aureus protein A (virulence factor)?

A

It binds the Fc region of IgG (Fc-IgG), inhibiting complement activation and phagocytosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Which drugs of the penicillin class are appropriate for treatment of Pseudomonas infection?

A

Extended-spectrum penicillins (eg, piperacillin, ticarcillin)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

A risk of enterohemorrhagic Escherichia coli (EHEC) contamination is typically associated with what foods?

A

Undercooked meats and raw leafy vegetables

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What pathogen causes leprosy, and from where do humans acquire it?

A

Mycobacterium leprae; mainly from infected humans (rarely, armadillos)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What findings (eg, morphology, lab results, growth temperature) help identify Campylobacter jejuni as a cause of infection?

A

Comma or S-shaped with polar flagella, oxidase ⊕, grows at 42°C (Campylobacter likes the hot campfire)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Overgrowth of what type of bacteria occurs in the vagina of a patient with bacterial vaginosis?

A

Anaerobic bacteria (including the pleomorphic, gram-variable Gardnerella vaginalis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

What are 2 common modes of transmission for Campylobacter jejuni?

A

Fecal-oral, through person-to-person contact; ingestion of contaminated poultry, meat, or milk; note that contact with infected animals (dogs, cats, pigs) is also a risk factor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

You add Streptococcus agalactiae to a culture of Staphylococcus aureus, which enlarges the area of hemolysis. What bacterial substance causes this finding?

A

CAMP factor made by S agalactiae (CAMP denotes the authors of the test, not cyclic AMP)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Name the 4 illnesses most commonly caused by infection with Streptococcus pneumoniae.

A

Meningitis, otitis media (in children), sinusitis, pneumonia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

A patient with dental caries has an abscess with sinus drainage that contains yellow “sulfur granules.” Where is this organism normally found?

A

The normal oral, reproductive, and GI flora; this is Actinomyces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

What is the strategy of management in a Bacillus cereus infection?

A

Supportive care; antibiotics are ineffective against toxins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

How do you confirm a Mycobacterium leprae infection?

A

M leprae is diagnosed by tissue polymerase chain reaction (PCR) or skin biopsy; it cannot be grown in vitro

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

Neisseria meningitidis and N gonorrhoeae both ferment what type of sugar and produce which type of immunoglobulin (Ig) protease?

A

Both ferment glucose and produce IgA protease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

What unique property of chlamydial cell walls makes β-lactam antibiotics ineffective?

A

Chlamydial cell walls lack classic peptidoglycan (have less muramic acid residues)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

How are gonococcal and meningococcal infections diagnosed?

A

Gonococcus: nucleic acid amplification test; meningococcus: culture-based tests or polymerase chain reaction (PCR)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

In the lab, you have a coagulase ⊖ Staphylococcus bacterium. You notice that it is novobiocin resistant. Identify it

A

NOvobiocin: Saprophyticus is Resistant; Epidermidis is Sensitive (NO StRESs on the office “staph” retreat)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

How would you differentiate Pseudomonas from other nonlactose fermenters?

A

It is oxidase positive; other nonlactose fermenters are oxidase ⊖

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

In a patient with virulent Mycobacterium tuberculosis infection, what inhibits phagolysosome fusion?

A

Sulfatides (surface glycolipids)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

Differentiate Legionnaires’ disease from Pontiac fever.

A

Legionnaires’ disease is marked by severe pneumonia (unilateral, lobar) with fever, CNS and GI symptoms; Pontiac fever is a mild, flu-like syndrome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

What stabilizes the membrane of Mycoplasma pneumoniae?

A

Sterols in the bacterial membranes; M pneumoniae lack cell walls

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

Which optochin-resistant bacteria, part of the normal oropharyngeal flora, cause dental caries?

A

Streptococcus mutans and Streptococcus mitis; Viridans group strep live in the mouth; they are not afraid of-the-chin (op-to-chin resistant)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

What is the last clinical stage of an infection caused by Bordetella pertussis?

A

Convalescent stage; gradual recovery from persistent cough

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

Which gene from the staphylococcal chromosomal cassette is involved in penicillin resistance?

A

mecA gene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

What diseases are caused by Chlamydia trachomatis?

A

Neonatal and follicular adult conjunctivitis, urethritis, pelvic inflammatory disease, and reactive arthritis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

Under the microscope, you observe gram ⊕, spore-forming, obligate anaerobic bacilli. Diagnosis?

A

Clostridium spp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

A child presents with acid-fast organisms in his blood and cervical lymphadenitis. If tuberculosis is ruled out, what is the likely cause?

A

Mycobacterium scrofulaceum infection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

How do levels of Shiga toxin compare between Shigella boydii, Shigella sonnei, Shigella dysenteriae, and Shigella flexneri?

A

Most to least: S dysenteriae > S flexneri > S boydii > S sonnei; invasion of M cells causes pathogenicity so even organisms that produce little toxin can cause disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

Describe the morphology of Leptospira interrogans.

A

Spirochete with hook-shaped ends

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

Name some conditions that are treated using local botulinum toxin A (Botox)

A

Focal dystonia, muscle spasms, hyperhidrosis, and cosmetic reduction of facial wrinkles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

How would you treat a patient with profuse rice-water diarrhea caused by gram ⊖ flagellated bacteria?

A

Oral rehydration therapy (diagnosis: Vibrio cholerae)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

In a woman who is 36 weeks pregnant, what bacterium should you screen for?

A

Streptococcus agalactiae colonizes the vagina and is screened for at 35-37 weeks of gestation with rectal and vaginal swabs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

Name the aerobic gram ⊕ bacilli.

A

Corynebacterium, Listeria, and Bacillus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

What medications would be used to treat the lepromatous form of leprosy (Hansen disease)?

A

Dapsone, rifampin, and clofazimine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

How does Staphylococcus epidermidis ferment mannitol?

A

It does not; S epidermidis cannot ferment mannitol (unlike Staphylococcus aureus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

What 2 tests can be used to diagnose infection with Helicobacter pylori?

A

Urea breath test and fecal antigen test

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

Where do viridans group streptococci commonly colonize in the human body?

A

The oropharynx

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

A 20-year-old pig farmer has bloody diarrhea. He later complains of dysuria and sore red knees. What happened? How did he get infected?

A

He has reactive arthritis from Campylobacter jejuni infection, most likely contracted from infected pigs (can also be acquired from dogs and cats)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

Describe the clinical presentation associated with Gardnerella vaginalis infections.

A

Gray discharge with a fishy odor; nonpainful (vs vaginitis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

What drugs are used to treat a patient with leprosy, low bacterial load, and a largely Th1-type immune response?

A

Dapsone and rifampin (diagnosis: tuberculoid leprosy)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

Name 3 types of infections caused by nontypeable strains of Haemophilus influenzae.

A

Otitis media, conjunctivitis, and bronchitis (all mucosal infections)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

A farm girl develops bloody diarrhea, abdominal cramps, nausea, vomiting, and fever. What is the likely diagnosis?

A

Salmonella spp infection (excluding S typhi)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

A patient with trismus, risus sardonicus, and opisthotonos comes to your office. He asks, “What could I have done to prevent this?”

A

Received a tetanus vaccine (most cases occur in unvaccinated individuals)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

How is anaplasmosis transmitted?

A

The Ixodes tick transmits Anaplasma spp from deer and mice

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

Evidence of what recent skin infection is noted on examination of a boy presenting with a puffy face and tea-colored urine?

A

Impetigo (“honey-crusted” lesions), which is caused by Streptococcus pyogenes and more commonly precedes glomerulonephritis than pharyngitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
79
Q

A patient who is immunocompromised has a pulmonary infection with an acid-fast bacteria. PPD test is negative; he has unusual skin lesions. Treatment of choice?

A

TMP-SMX; he may have a severe Nocardia infection, which can mimic TB but with negative PPD findings; can cause cutaneous infections after trauma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
80
Q

Which bacteria are responsible for endemic typhus and epidemic typhus, and how are they transmitted?

A

Endemic: Rickettsia typhi, transmitted via fleas Epidemic: Rickettsia prowazekii, transmitted via human body louse

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
81
Q

Besides Neisseria gonorrhoeae, which gram ⊖ aerobic diplococci do not use maltose?

A

Moraxella

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
82
Q

Tabes dorsalis with general paresis may present in which stage of syphilis?

A

Tertiary syphilis; this is neurosyphilis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
83
Q

How would you prevent disease transmission of Neisseria gonorrhoeae?

A

Condoms decrease sexual transmission; erythromycin ointment prevents neonatal blindness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
84
Q

Of α-hemolytic cocci, which are bile soluble and insoluble?

A

Streptococcus pneumoniae is bile soluble; viridans streptococci are bile insoluble

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
85
Q

What 2 clinical syndromes are caused by Legionella?

A

Legionnaires’ disease and Pontiac fever

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
86
Q

What are the symptoms of Mycoplasma pneumoniae pneumonia?

A

Atypical “walking pneumonia”; insidious onset with nonproductive cough, headache, and patchy or diffuse interstitial infiltrates on chest x-ray

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
87
Q

Name 4 diseases caused by Haemophilus influenzae infection.

A

Epiglottitis, Meningitis, Otitis media, and Pneumonia (caused by HaEMOPhilus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
88
Q

An unvaccinated patient has pseudomembranous pharyngitis with lymphadenopathy. What is the treatment?

A

Antibiotic therapy +/- diphtheria antitoxin (the patient has diphtheria infection)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
89
Q

An infant who is fed breast milk mixed with honey and jaggery presents with ↓ tone in all limbs. How would you treat the condition?

A

Treat with human botulinum immunoglobulin (the infant likely has botulism)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
90
Q

What 3 illnesses can Klebsiella cause?

A

Aspiration pneumonia in alcoholics and diabetics, abscesses in lungs and liver, nosocomial UTIs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
91
Q

A bird trader who experiences fever and dyspnea is found to have an atypical pneumonia. What pathogen is the most likely cause?

A

A bird trader who experiences fever and dyspnea is found to have an atypical pneumonia. What pathogen is the most likely cause? flip_to_backCLICK FOR ANSWERbookmark_borderthumb_upthumb_down Chlamydophila psittaci, which has an avian reservoir (parrots) and causes atypical pneumonia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
92
Q

Which form of leprosy presents with hypoesthetic, hairless skin nodules?

A

Tuberculoid leprosy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
93
Q

Describe the Gram staining, hemolysis, and unique antibiotic resistance pattern(s) of viridans group streptococci.

A

Gram ⊕, α-hemolytic cocci, resistant to optochin and bile insoluble (unlike Streptococcus pneumoniae)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
94
Q

How does a streptococcal strain that shows complete hemolysis and has PYR ⊖ status react to bacitracin?

A

It is bacitracin resistant; this is group B (Streptococcus agalactiae) beta-hemolytic streptococci

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
95
Q

What staining property do all mycobacteria have in common?

A

All are gram ⊕, acid-fast rods

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
96
Q

In which 3 populations can Listeria monocytogenes infection lead to meningitis, and what is the empiric treatment of meningitis for them?

A

Neonates, immunocompromised patients, and older adults; ampicillin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
97
Q

A man presents with lockjaw and spasms. A few days ago, he suffered a wound while playing football in the mud. How would you treat him?

A

Treat a Clostridium tetani infection with antitoxin ± vaccine booster, diazepam (for muscle spasms), antibiotics, and wound debridement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
98
Q

Staphylococcus aureus most commonly colonizes which parts of the body?

A

The nares, axilla, ears, and groin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
99
Q

What laboratory tests can be done that indicate a recent Streptococcus pyogenes infection?

A

ASO titer and anti-DNase B antibodies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
100
Q

What are 2 ways to directly test for syphilis?

A

Darkfield microscopy and polymerase chain reaction (PCR)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
101
Q

In what medium is Legionella pneumophila grown in vitro?

A

Charcoal yeast extract medium with iron and cysteine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
102
Q

What immunologic diseases result from Streptococcus pyogenes pharyngitis?

A

Rheumatic fever, glomerulonephritis (“Ph”yogenes pharyngitis can result in rheumatic “phever” and glomerulonephritis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
103
Q

Helicobacter pylori is triple ⊕ for what 3 enzymes?

A

Catalase, oxidase, and urease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
104
Q

What 2 vaccination options are available to prevent Salmonella typhi infection?

A

Oral vaccine with live attenuated S typhi and IM vaccine with Vi capsular polysaccharide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
105
Q

Name 11 conditions/properties associated with Pseudomonas infection using the PSEUDOMONAS mnemonic.

A

Pneumonia, Sepsis, Ecthyma gangrenosum, UTIs, Diabetes, Osteomyelitis, Mucoid polysaccharide capsule, Otitis externa, Nosocomial infections, Addicts (drug abusers), Skin infections

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
106
Q

Shiga-like toxin can cause hemolytic-uremic syndrome, which is a triad of…

A

Anemia, thrombocytopenia, acute kidney injury

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
107
Q

How would the presentation be different if a patient had Staphylococcus aureus toxic shock syndrome (TSS) versus Streptococcus pyogenes TSS?

A

S aureus TSS: fever, vomiting, shock, desquamation, rash, and end-organ failure; S pyogenes TSS: painful skin infection (atypical presentation) with ARDS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
108
Q

What symptoms and incubation period are associated with the diarrheal type of Bacillus cereus infection?

A

Nonbloody, watery diarrhea and gastrointestinal pain that arises 8-18 hours after ingestion of contaminated foods

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
109
Q

What pathogen is found in unpasteurized dairy products and can cause recurrent rising and falling fevers?

A

Brucella spp (brucellosis), which causes undulating fevers from unpasturized dairy products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
110
Q

What is the life-threatening complication that can occur in a patient with Clostridium difficile diarrhea?

A

Toxic megacolon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
111
Q

What drug could prevent disseminated Mycobacterium avium–intracellulare infection in a patient with AIDS?

A

Azithromycin, which is used for prophylaxis, particularly in patients with AIDS when the CD4+ count is <50 cells/mm3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
112
Q

Describe the symptoms seen in pulmonary anthrax most commonly due to inhalation of spores from contaminated animals or animal products.

A

Flu-like symptoms, rapidly progressing to fever, mediastinitis, pulmonary hemorrhage, and shock

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
113
Q

How would you describe the lesions generated by Actinomyces?

A

Oral/facial abscesses that drain through sinus tracts; drainage contains yellow “sulfur granules”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
114
Q

A farmer has cycling fevers, night sweats, and arthralgias after drinking unpasteurized milk. What is the causative organism?

A

Brucella (the farmer likely has brucellosis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
115
Q

What 2 outcomes could be expected after a primary tuberculosis infection?

A

Recovery (>90%): fibrous healing/calcification, PPD test ⊕; progressive primary TB (<10%): seen in patients with AIDS or malnutrition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
116
Q

Describe Argyll Robertson pupils.

A

A pupil that constricts with accommodation but does not react to light (seen in tertiary syphilis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
117
Q

What are some conditions that can result from toxin dissemination in diphtheria?

A

Myocarditis, arrythmias, neuropathies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
118
Q

You culture a cellulitis sample, which yields catalase ⊕ cocci. How can you differentiate the 3 main species in this group?

A

Staphylococcus aureus is coagulase ⊕; coagulase ⊖ species: Staphylococcus epidermidis is novobiocin sensitive and Staphylococcus saprophyticus is resistant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
119
Q

What lab findings are expected when Staphylococcus saprophyticus is grown in a culture?

A

Gram ⊕, catalase ⊕, coagulase ⊖, urease ⊕ cocci in clusters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
120
Q

What lab test can differentiate enterocci from nonenterococcal group D bacteria?

A

Enterococci grow in 6.5% sodium chloride and bile; nonenterococcal group D bacteria cannot

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
121
Q

What are the drugs used to treat a gonococcal infection?

A

Ceftriaxone (plus azithromycin or doxycycline for concurrent chlamydial coinfection)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
122
Q

Reactivation of Mycobacterium tuberculosis in a partially immune, hypersensitized host leads to what kind of infection?

A

Secondary tuberculosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
123
Q

What differentiates Q fever from the diseases of the Rickettsia genus, to which it is closely related?

A

Q fever, caused by Coxiella Burnetii, can survive outside in endospore form; there is no rash or vector (Q fever is a Quite Complicated Bug)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
124
Q

What are the 2 forms of Hansen disease?

A

Lepromatous and tuberculoid (Hansen disease is also known as leprosy)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
125
Q

What bacteria is found in animal urine and often contaminates public recreational water supplies?

A

Leptospira spp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
126
Q

What determines the virulence of Streptococcus pneumoniae?

A

Capsule (virulence is lost in its absence)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
127
Q

What toxigenic diseases result from infection with Streptococcus pyogenes?

A

Scarlet fever, necrotizing fasciitis, toxic shock-like syndrome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
128
Q

Which Mycobacterium species presents with hand infection, and how is it acquired?

A

Mycobacterium marinum; acquired through aquatic exposure, likely through aquarium handling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
129
Q

A patient contracts an infection at the hospital by a gram ⊕ bacteria that are notably resistant to vancomycin therapy. Most likely causative organism?

A

Vancomycin-resistant enterococci (VRE), a major cause of nosocomial infections

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
130
Q

What symptoms would you observe in a patient in the third (late disseminated) stage of Lyme disease?

A

Encephalopathy, chronic arthritis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
131
Q

Which 2 bacteria are slow lactose-fermenting gram ⊖ bacilli?

A

Citrobacter and Serratia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
132
Q

What populations are most likely to experience a Mycoplasma pneumoniae outbreak?

A

Individuals <30 years of age, military recruits, college students, and inmates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
133
Q

What histologic finding is characteristic of the lesions associated with Brucella infection?

A

Noncaseating granulomas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
134
Q

A febrile patient with jaundice complains of RUQ tenderness after an endoscopic retrograde cholangiopancreatography (ERCP) procedure. What is the causative organism?

A

Enterococci; diagnosis is ascending cholangitis (enterococci are a common cause of biliary tract infection after gastrointestinal/genitourinary [GI/GU] procedures)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
135
Q

What toxins are responsible for traveler’s diarrhea?

A

Heat-labile and heat-stable enteroToxins of Enterotoxigenic Escherichia coli (ETEC) cause Traveler’s diarrhea (watery)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
136
Q

What 2 conditions may bring about a false negative PPD test result?

A

Sarcoidosis or HIV (with low CD4+ counts) may show a ⊖ PPD test result despite active disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
137
Q

What are the common routes of transmission of Listeria monocytogenes to a newborn?

A

Transplacental transmission and vaginal transmission during delivery

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
138
Q

A child has gray-white membranes adhering to his pharynx and diffuse lymphadenopathy. How do you culture the suspected infectious agent?

A

Use cystine-tellurite agar; Corynebacterium diphtheriae will grow black colonies (gray-white membranes indicate pseudomembranous pharyngitis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
139
Q

Describe the appearance of α, β, and γ hemolysis on agar.

A

α: partial (green); β: complete (clear); γ: absent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
140
Q

A medical student finds gram ⊕ spherical bacteria appearing in clusters. What is the most likely strain?

A

Staphylococcus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
141
Q

How does the rash caused by Rickettsia rickettsii spread on the body?

A

Rash usually starts at ankles and wrists and then spreads to trunk, palms, and soles; “Ricketsii on the wRists, Typhus on the Trunk”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
142
Q

How do you classify β-hemolytic streptococci based on their PYR status?

A

Group A (Streptococcus pyogenes) is PYR ⊕; group B (Streptococcus agalactiae) is PYR ⊖

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
143
Q

Name 6 inflammatory diseases that can result from infection with Staphylococcus aureus.

A

Skin infection, endocarditis, pneumonia (often following influenza virus infection), organ abscess, septic arthritis, and osteomyelitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
144
Q

Gram ⊖ bacilli are differentiated by their ability to ferment what substance?

A

Lactose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
145
Q

What abnormal values will you see on labs in a patient with staphylococcal toxic shock syndrome?

A

↑ AST, ↑ ALT, ↑ bilirubin levels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
146
Q

What 2 risk factors are associated with staphylococcal toxic shock syndrome?

A

Prolonged use of vaginal tampons or nasal packing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
147
Q

What 2 diseases are associated with Bartonella infections in patients who are immunocompromised?

A

Bacillary angiomatosis and cat scratch disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
148
Q

What is the initial treatment for a Helicobacter pylori infection?

A

Triple therapy: Amoxicillin (metronidazole if allergic to penicillin), Clarithromycin, Proton pump inhibitor (Antibiotics Cure Pylori)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
149
Q

Why does Neisseria gonorrhoeae not have a vaccine?

A

Due to antigenic variation of pilus proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
150
Q

What subtype of Streptococcus bovis is most strongly associated with colon cancer?

A

Streptococcus gallolyticus, biotype 1 of S bovis (Bovis in the blood = cancer in the colon)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
151
Q

How does hemolytic-uremic syndrome develop following an infection with enterohemorrhagic Escherichia coli (EHEC)?

A

EHEC releases Shiga-like toxin → microthrombi form and damage endothelium → RBC hemolysis (shistocytes), ↓ platelets, and ↓ renal blood flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
152
Q

What bacterium is transmitted by fleas and causes plague in humans?

A

Yersinia pestis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
153
Q

What is latent syphilis, and when does it occur?

A

Latent syphilis is characterized by positive serology but no symptoms; it follows secondary syphilis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
154
Q

In the lab you find an oxidase ⊕, curved, gram ⊖ bacterium that is able to produce urease. What is the likely culprit?

A

Helicobacter pylori

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
155
Q

You culture a sputum sample, suspecting either Staphylococcus or Streptococcus. How can you differentiate the bacteria?

A

Staphylococcus is catalase ⊕ and grows in clusters; Streptococcus is catalase ⊖ and grows in pairs or chains (both are gram ⊕ cocci)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
156
Q

A chest x-ray of a 70-year-old man with a cough shows left lower lobe pneumonia. What hemolysis pattern does the most likely pathogen exhibit?

A

Green, partial hemolysis (α-hemolysis); Streptococcus pneumoniae is the most common cause of pneumonia in older patients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
157
Q

In a patient with Mycoplasma pneumoniae, why are you unable to observe bacteria on a Gram stain?

A

M pneumoniae lack cell walls, so are not seen on a Gram stain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
158
Q

What vector is responsible for the transmission of ehrlichiosis and anaplasmosis?

A

Tick

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
159
Q

In what population infected with tuberculosis is progressive lung disease most likely to occur?

A

Individuals who are malnourished, immunocompromised, and/or HIV ⊕

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
160
Q

A patient presents with fever, abdominal pain, constipation, and rose-colored spots on his abdomen. What is the causative agent?

A

Salmonella typhi (diagnosis is typhoid fever)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
161
Q

What organism is the likely pathogen if osteomyelitis develops following a puncture wound, especially in patients with diabetes?

A

Pseudomonas aeruginosa (a common cause of osteomyelitis after a puncture wound)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
162
Q

How long does Staphylococcus aureus toxin take to cause nonbloody diarrhea and emesis?

A

Preformed Staphylococcal enterotoxins causing food poisoning have a short incubation period of 2-6 hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
163
Q

In the lab, you discover an oxidase ⊕, comma-shaped, gram ⊖ organism that grows in alkaline media. Identify this bacterium.

A

Vibrio cholerae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
164
Q

A newborn comes to the NICU with a staccato cough and eye discharge. You notice significant eosinophilia on lab studies. What is the cause?

A

Chlamydia trachomatis, types D-K

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
165
Q

What pathogen is responsible for Rocky Mountain spotted fever?

A

Rickettsia rickettsii, transmitted via tick

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
166
Q

In what states is Rocky Mountain spotted fever commonly found?

A

South Atlantic states, especially North Carolina (despite its name)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
167
Q

A gram positive bacterium growing in chains shows no hemolysis and grows in 6.5% NaCl. What is its PYR status?

A

PYR ⊕; this is Entercoccus species (eg, Enterococcus faecium, Enterococcus faecalis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
168
Q

Lobar pneumonia with “currant jelly” sputum develops in a patient who aspirated his own vomit. Chest x-ray is concerning for an abscess. What is the most likely pathogen?

A

Klebsiella (ABCDE’s of Klebsiella = Aspiration pneumonia, aBscess in lungs and liver, “Currant jelly” sputum, Diabetics, EtOH abuse)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
169
Q

What animal reservoirs are the source of disease in those afflicted with plague?

A

Rats and prairie dogs; transmit Yersinia pestis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
170
Q

Name organisms that are gram ⊖ coccobacilli.

A

Haemophilus influenzae, Bordetella pertussis, Francisella tularensis, Pasteurella, Brucella, Acinetobacter baumannii

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
171
Q

What are the 2 virulence factors of Streptococcus pneumoniae?

A

IgA protease and its capsule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
172
Q

Explain the mechanism through which viridans group streptococci cause subacute bacterial endocarditis.

A

Streptococcus sanguinis produces dextrans, which bind fibrin-platelet aggregates on damaged heart valves and cause subacute bacterial endocarditis (sanguinis = blood, in the heart)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
173
Q

What 2 characteristics differentiate Actinomyces from Nocardia?

A

Actinomyces are anaerobes and acid fast ⊖; Nocardia are weakly acid-fast aerobes. Both are gram ⊕ and form long, branching filaments resembling fungi

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
174
Q

How does Salmonella spread through the body as compared to Shigella?

A

Salmonella spreads hematogenously, whereas Shigella spreads from cell to cell without hematogenous spread

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
175
Q

Typically, what part of the body does the gram ⊕ cocci Streptococcus bovis colonize?

A

The gut

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
176
Q

What hematologic finding may help confirm Mycoplasma pneumoniae infection?

A

A high titer of cold agglutinins (IgM); they can agglutinate or lyse red blood cells (Mycoplasma gets cold without a coat)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
177
Q

Name the enzyme produced by Escherichia coli that breaks down lactose into glucose and galactose.

A

β-galactosidase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
178
Q

What organism causes Q fever, and how is it transmitted?

A

Coxiella burnetii; transmitted by spores from bovine/ovine amniotic fluid inhaled as aerosols (no arthropod vector)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
179
Q

For which Neisseria species is a vaccine available?

A

N meningitidis (type B vaccine, available for individuals at risk)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
180
Q

What 2 factors help Streptococcus pyogenes impair host phagocytosis?

A

The hyaluronic acid capsule and M protein inhibit phagocytosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
181
Q

What is the vector for the pathogen that causes Lyme disease?

A

Ixodes ticks that dwell on deer and mice

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
182
Q

How does staphylococcal food poisoning present?

A

Usually presents with nonbloody diarrhea and emesis 2-6 hours after ingestion of food with preformed toxin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
183
Q

In a patient with virulent Mycobacterium tuberculosis infection, what specific bacterial factor activates macrophages?

A

Cord factor, which causes a “serpentine cord” appearance in virulent strains and activates macrophages

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
184
Q

Your culture of gram ⊕, catalase ⊖ cocci exhibits no hemolysis. How will you further identify the species?

A

Nonenterococci species (eg, Streptococcus bovis) cannot grow in 6.5% NaCl and are PYR ⊖; enterococci (Enterococcus faecium, Enterococcus faecalis) can grow in 6.5% NaCl and are PYR ⊕

185
Q

What are the classical symptoms of tuberculosis?

A

Night sweats, weight loss, fever, hemoptysis, cough (productive or nonproductive)

186
Q

Which bacteria produce H2S on triple sugar iron (TSI) agar?

A

Salmonella and Proteus

187
Q

A bacteria is identified to be hippurate test ⊕, PYR ⊖, bacitracin resistant, and β-hemolytic. Name the bacteria.

A

Streptococcus agalactiae

188
Q

What 3 clinical conditions usually follow Neisseria meningitidis infection?

A

Meningococcemia, meningitis, and Waterhouse-Friderichsen syndrome

189
Q

When does neonatal conjunctivitis from gonorrhea present?

A

2-5+ days after birth

190
Q

Which Chlamydia trachomatis serotypes cause urethritis, pelvic inflammatory disease (PID), ectopic pregnancy, neonatal pneumonia with eosinophilia, and neonatal conjunctivitis?

A

Types D-K

191
Q

What are the symptoms of Q fever?

A

Headache, cough, flu-like symptoms, pneumonia, possibly with hepatitis; may also present as culture ⊖ endocarditis

192
Q

A 5-year-old boy develops bloody diarrhea after eating raw beef. Two weeks later, he cannot move his legs and has hyporeflexia. What happened?

A

He likely has Guillain-Barré syndrome triggered by Campylobacter jejuni infection

193
Q

What type of lesion is seen on an x-ray of the lung fields of a patient with secondary tuberculosis?

A

A fibrocaseous cavitary lesion in the upper lobe

194
Q

What are the reservoirs for Shigella and Salmonella?

A

All strains of Salmonella except S typhi have human and animal reservoirs; Shigella and S typhi have human reservoirs only

195
Q

Which bacteria that frequently causes atypical pneumonia can cause an atypical variant of Stevens-Johnson syndrome in children and adolescents?

A

Mycoplasma pneumoniae

196
Q

What 4 shapes are most gram ⊖ organisms classified as?

A

Diplococci, coccobacilli, bacilli, and curved rods

197
Q

What disease does Rickettsia prowazekii cause, and what is its vector?

A

Epidemic typhus; body lice

198
Q

How is Bartonella spp transmitted?

A

Through a cat scratch

199
Q

A patient is diagnosed with peptic ulcer disease secondary to infection with Helicobacter pylori. The organism is found to be resistant to macrolides. Treatment?

A

Bismuth-based quadruple therapy

200
Q

What symptoms would you observe in a patient in the second (early disseminated) stage of Lyme disease?

A

Secondary lesions, atrioventricular block, carditis, migratory myalgias/transient arthritis, facial nerve (Bell) palsy

201
Q

In the lab you see a strain of Streptococcus showing partial hemolysis. If the bacteria are optochin resistant, what is the strain?

A

Optochin: Viridans is Resistant, but Pneumoniae is Sensitive (OVRPS [overpass])

202
Q

How can you distinguish enterohemorrhagic Escherichia coli (EHEC) from other strains using a culture?

A

EHEC does not ferment sorbitol whereas other strains do

203
Q

How do you diagnose disease in a patient with suspected Clostridium difficile infection (marked by diarrhea after antibiotic use)?

A

Diagnosed by polymerase chain reaction (PCR) or antigen detection of one or both toxins in stool

204
Q

What 3 spirochete species most commonly infect humans?

A

Borrelia, Leptospira, and Treponema (BLT)

205
Q

A 30-year-old on long-term antibiotics develops a severe watery diarrheal illness with abdominal pain. Two toxins are detected in his stool. How do the toxins cause his symptoms?

A

He likely has Clostridium difficile infection, which releases toxins A and B into the stool, leading to watery diarrhea and pseudomembranous colitis

206
Q

What antibiotic are the bacteria Enterococcus faecalis normally resistant to?

A

Penicillin G

207
Q

What type of hemolysis is induced by Enterococcus species?

A

Enterococcus species exhibit variable hemolysis

208
Q

What is the source of the spirochete Leptospira interrogans?

A

Water contaminated with animal urine; the disease is particularly prevalent in the tropics (eg, Hawaii) and among surfers

209
Q

Which cephalosporins can be used to treat a Pseudomonas aeruginosa infection?

A

Third- and fourth-generation cephalosporins (eg, ceftazidime, cefepime)

210
Q

What Escherichia coli virulence factor is responsible for development of septic shock?

A

LPS endotoxin

211
Q

A boy with a new pet turtle has gastroenteritis and bloody diarrhea. Name the causative agent and possible sources of infection.

A

Salmonella spp; eggs, poultry, turtles, and other pets are sources

212
Q

A patient with pseudomembranous pharyngitis and arrhythmias has diphtheria. What is the toxin, and how does it inhibit protein synthesis?

A

Exotoxin (encoded on a β-prophage); it inhibits protein synthesis by adenosine diphosphate- (ADP) ribosylation of elongation factor 2 (EF-2)

213
Q

Reptiles and poultry are the animal hosts of what pathogen that causes a diarrheal illness?

A

Salmonella spp (exception: S typhi)

214
Q

What is responsible for the recurrent nature of the fever in Borrelia recurrentis infections?

A

Variation in bacterial surface antigens (Borrelia recurrentis causes relapsing fever)

215
Q

How do the pathogenic mechanisms of dysentery differ between enterohemorrhagic Escherichia coli (EHEC) and enteroinvasive E coli (EIEC)?

A

EHEC produces a Shiga-like toxin, causing necrosis and inflammation; EIEC directly invades the mucosa, causing necrosis and inflammation

216
Q

Which fluoroquinolones can be used to treat a Pseudomonas aeruginosa infection?

A

Ciprofloxacin or levofloxacin

217
Q

A 9-year-old boy has ascending weakness and joint pain. If this is related to an infection, what did he most likely eat to cause it?

A

Contaminated poultry, meat, or unpasteurized milk (can harbor Campylobacter jejuni, an antecedent to Guillain-Barré syndrome and reactive arthritis)

218
Q

What population groups are at risk of Legionella pneumophila infection?

A

Smokers and patients with chronic lung disease

219
Q

What culture medium could you use to grow Mycoplasma pneumoniae?

A

Eaton agar

220
Q

A man who swims in a cove has fever, fatigue, body aches, photophobia, and conjunctival suffusion. What is the water contaminated with?

A

Animal urine containing Leptospira interrogans; diagnosis: leptospirosis

221
Q

Gram ⊖, aerobic coccobacilli infect a young child and cause whooping cough. What class of antibiotics could be used for treatment?

A

Macrolides (use TMP-SMX if allergic to macrolides)

222
Q

Why are Chlamydia species obligate intracellular organisms?

A

They cannot make their own ATP

223
Q

In what region of the United States is Lyme disease common?

A

The northeastern United States

224
Q

What symptoms are seen in the paroxysmal phase of Bordetella pertussis infection?

A

Paroxysms of intense cough preceding an inspiratory “whooP,” posttussive vomiting

225
Q

What treatment do you typically use for rickettsial diseases and vector-borne illnesses?

A

Doxycycline

226
Q

What antibiotics are used to treat infection with Salmonella typhi and other Salmonella species?

A

Salmonella typhi: ceftriaxone or fluoroquinolone Salmonella spp. (except S typhi): antibiotics not indicated

227
Q

To what condition is a female with an intrauterine device at risk if she has a confirmed Actinomyces infection?

A

Pelvic inflammatory disease (PID), which can be caused by Actinomyces in women with IUDs

228
Q

A lab tech notes brownish-greenish rings around colonies on blood agar. Which 2 gram ⊕ cocci might these be?

A

Streptococcus pneumoniae and viridans streptococci

229
Q

What is the definition of zoonosis?

A

The transmission of an infectious disease between animals and humans

230
Q

Compare the infectious dose (ID50) of Salmonella to that of Shigella.

A

Salmonella has a high ID50 (large inoculum needed; acid-labile) Shigella has a low ID50 (small inoculum needed; acid-stable)

231
Q

What is the relationship between Haemophilus influenzae and the flu?

A

There is no relationship; it is the influenza virus that causes the flu

232
Q

What organism causes Hansen disease?

A

Also known as leprosy, it is caused by Mycobacterium leprae, an acid-fast bacillus

233
Q

What property of Pseudomonas may contribute to the chronic pneumonia in patients with cystic fibrosis?

A

The mucoid polysaccharide capsule causes chronic pneumonia in patients with cystic fibrosis as a result of biofilm formation

234
Q

What is the mechanism by which methicillin-resistant Staphylococcus aureus (MRSA) exhibits resistance to penicillins like methicillin?

A

Resistance is due to altered penicillin-binding protein

235
Q

Neisseria diplococci are isolated from a patient experiencing a severe inflammatory response. What virulence factor is causing these symptoms?

A

Lipooligosaccharides, which have potent endotoxin activity

236
Q

What are the 2 modes of transmission of Bacillus anthracis?

A

Cutaneous exposure and inhalation

237
Q

What 3 diseases start with a rash on the palms and soles?

A

Coxsackievirus A infection, Rocky Mountain spotted fever, and secondary Syphilis (you drive CARS using your palms and soles)

238
Q

By what route does Haemophilus infection spread?

A

Aerosol transmission

239
Q

In the lab, you see a strain of Streptococcus with partial hemolysis. If the bacteria are optochin sensitive, what is the specific strain?

A

Optochin: Viridans is Resistant, Pneumoniae is Sensitive (OVRPS [overpass])

240
Q

What structural changes might result from local tissue destruction by secondary tuberculosis?

A

Cavitation, caseation, and scar formation

241
Q

How does the rash in epidemic typhus spread?

A

Starts centrally and spreads out; spares palms and soles; “Ricketsii on the wRists, Typhus on the Trunk”

242
Q

An unvaccinated boy contracts meningitis from Haemophilus influenzae. Treatment?

A

Treat with ceftriaxone for Haemophilus influenzae meningitis; close contacts should receive rifampin prophylaxis

243
Q

Name 4 clinically important mycobacteria that cause tuberculosis-like illnesses.

A

Mycobacterium tuberculosis, Mycobacterium scrofulaceum, Mycobacterium avium–intracellulare, and Mycobacterium marinum

244
Q

A patient tells you that he started vomiting about an hour after eating reheated rice. What is the most likely causative toxin?

A

Cereulide, the preformed toxin in Bacillus cereus (patient has reheated rice syndrome)

245
Q

What is the characteristic fever that Brucella causes?

A

Undulant fever (undulating fever from unpasteurized milk)

246
Q

What Escherichia coli virulence factor is responsible for development of pneumonia and neonatal meningitis?

A

K capsule

247
Q

In what 4 ways can Shigella be transmitted between humans?

A

The Four F’s = Fingers, Flies, Food, and Feces

248
Q

Describe the Gram stain and morphology of Klebsiella.

A

Gram ⊖ rod

249
Q

What are the 3 virulence factors of Bordetella pertussis?

A

Tracheal cytotoxin, pertussis toxin (disables Gi), adenylate cyclase toxin (↑ cAMP)

250
Q

Describe Chlamydiae’s 2 life forms.

A

Elementary body Enters cell by Endocytosis (“Enfectious”)​​​​​​ → turns into reticulate body; Reticulate body Replicates in cell by fission → Reorganize into elementary bodies

251
Q

Which animal acts as a reservoir of Mycobacterium leprae in the United States?

A

Armadillos

252
Q

What is the shape and Gram stain status of Listeria monocytogenes?

A

Listeria monocytogenes is a gram ⊕ rod

253
Q

A baby who was recently fed honey now shows signs of floppy baby syndrome. Ingestion of what substance caused the symptoms?

A

Honey, containing Clostridium botulinum spores; can cause floppy baby syndrome

254
Q

How does enteropathogenic Escherichia coli (EPEC) cause diarrhea?

A

It adheres to the apical surface and flattens villi, decreasing absorption

255
Q

What 2 patient populations are susceptible to Streptococcus pneumoniae sepsis?

A

Patients with sickle cell disease and asplenia

256
Q

What property of Staphylococcus epidermidis allows it to easily infect prosthetic devices (eg, hip implants, heart valves) and intravenous catheters?

A

Production of an adherent biofilm

257
Q

Describe the immune response to Salmonella or Shigella species.

A

Both Salmonella and Shigella primarily have a PMN response, but Salmonella typhi has a monocytic response

258
Q

A pregnant woman has vaginal colonies of Streptococcus agalactiae. What 3 diseases is her baby at risk of developing if the mother isn’t treated?

A

Group B streptococcal infection, which causes pneumonia, meningitis, and sepsis in Babies

259
Q

What vaccinations can prevent whooping cough?

A

Tdap or DTaP vaccines (protect against Bordetella pertussis)

260
Q

What rickettsial organism is commonly responsible for culture ⊖ endocarditis?

A

Coxiella burnetii

261
Q

A Streptococcus culture exhibits partial (α, green) hemolysis. How will you further categorize the species?

A

Viridans streptococci: no capsule, optochin resistant, bile insoluble; Streptococcus pneumoniae: capsule present, optochin sensitive, bile soluble

262
Q

Why is penicillin ineffective as a therapy option for Mycoplasma pneumoniae?

A

M pneumoniae, lacking cell walls, is resistant to penicillin

263
Q

What are 2 serologic tests that are nonspecific and used to screen for syphilis?

A

Veneral Disease Research Laboratory (VDRL) and rapid plasma reagin (RPR) tests

264
Q

How is Campylobacter jejuni transmitted?

A

Fecal-oral transmission (eg, pet feces, contaminated food, contact with hands of infected persons)

265
Q

How does Listeria monocytogenes avoid the immune system?

A

It forms “rocket tails” by means of actin polymerization, allowing movement through cell membranes while avoiding host antibodies

266
Q

A woman diagnosed wih bacterial vaginosis is prescribed metronidazole but cannot tolerate it. What second medication may be given instead?

A

Clindamycin is a reasonable second-line treatment (overgrowth of vaginal anaerobic bacteria due to ↓ lactobacilli characterize bacterial vaginosis)

267
Q

What population is typically affected by enteropathogenic Escherichia coli (EPEC) infections?

A

Children (EPEC = Pediatrics)

268
Q

In a patient with Mycoplasma pneumoniae pneumonia, how does the chest x-ray finding compare to the severity of clinical illness?

A

X-ray usually looks worse than the patient

269
Q

A patient who has had the bacille Calmette-Guérin (BCG) vaccine is being evaluated for tuberculosis. What is the most appropriate test to order?

A

Interferon-γ release assay (IGRA), a more specific test that yields fewer false ⊕ results than PPD yields from BCG vaccination

270
Q

What symptoms are seen in the catarrhal phase of Bordetella pertussis infection?

A

Coryza (catarrhal), low-grade fevers

271
Q

A 27-year-old man has spastic paralysis. Renshaw cell neurotransmitter release is inhibited. Name the toxin, and explain how it works.

A

Tetanospasmin exotoxin (from Clostridium tetani); cleaves SNARE proteins, thus blocking release of glycine and γ-aminobutyric acid (GABA), which are inhibitory neurotransmitters

272
Q

What are the key signs and symptoms of Lyme disease? (Hint: Lyme [lime] pie to the FACE)

A

Facial nerve palsy (usually bilateral), Arthritis, Cardiac block, Erythema migrans

273
Q

How can you distinguish between the 2 distinct Neisseria species based on their metabolism?

A

N meningitidis ferments maltose; N gonorrhoeae does not ferment maltose

274
Q

What specific finding on chest x-ray confirms primary tuberculosis?

A

Ghon complex (Ghon focus, typically in mid/lower lobes of the lung, with hilar node involvement)

275
Q

What bacterium causes Lyme disease?

A

Borrelia burgdorferi

276
Q

Where, geographically, are Chlamydia trachomatis serotypes A, B, and C found, and what diseases do they cause?

A

Africa; cause Blindness and result in Chronic infection; (ABC)

277
Q

Name the toxin produced by Bacillus anthracis and its components

A

Anthrax toxin, which is an exotoxin consisting of protective antigen, edema factor, and lethal factor

278
Q

Which organism is likely responsible for corneal ulcers in contact lens wearers?

A

Pseudomonas aeruginosa; causes corneal ulcers/keratitis and minor eye trauma

279
Q

You have a culture of gram ⊕, catalase ⊖ cocci that are γ-hemolytic and fail to grow in 6.5% NaCl. Do they grow in bile?

A

Yes; these are nonenterococcus bacteria (eg, Streptococcus bovis), which will grow in bile

280
Q

What spirochete is responsible for causing syphilis?

A

Treponema pallidum

281
Q

Antibodies to which virulent component of Streptococcus pyogenes can give rise to rheumatic fever?

A

M protein (antibodies enhance host defense, but can give rise to rheumatic fever)

282
Q

Why does infection with Yersinia enterocolitica often present in a manner similar to appendicitis?

A

The bacterium causes mesenteric adenitis and/or terminal ileitis, producing right lower quadrant abdominal pain

283
Q

A man has gram ⊕ cocci that grow normally in the colon and are penicillin G resistant. What do PYR and catalase testing yield?

A

Enterococci are catalase ⊖ and PYR ⊕

284
Q

Which form of Staphylococcus aureus is an important cause of serious nosocomial and community-acquired infections?

A

Methicillin-resistant Staphylococcus aureus (MRSA)

285
Q

Where does Staphylococcus saprophyticus normally inhabit the human body?

A

The female genital tract and perineum

286
Q

What tests can confirm the most likely diagnosis of a patient with a broad-based gait, ⊕ Romberg sign, and Argyll Robertson pupils?

A

VDRL, FTA-ABS, or PCR of spinal fluid (diagnosis: neurosyphilis)

287
Q

How do you treat a chlamydial infection?

A

Azithromycin (single dose) or doxycycline, plus ceftriaxone for possible concomitant gonorrhea

288
Q

In which host cell type do bacterial microcolonies form when a patient is infected with ehrlichiosis?

A

Monocytes; Monocytes for Ehrlichiosis; Granulocytes for Anaplasma (MEGA berry)

289
Q

What 5 disease states might Neisseria gonorrhoeae present as?

A

Gonorrhea, pelvic inflammatory disease (PID), septic arthritis, Fitz-Hugh–Curtis syndrome, and neonatal conjunctivitis (2-5 days after birth)

290
Q

Name the virulence factor(s) of Salmonella?

A

Endotoxin (Salmonella typhi has an additional virulence factor, Vi capsule)

291
Q

The Venereal Disease Research Laboratory (VDRL) test detects antibodies that have formed against which molecule?

A

Beef cardiolipin

292
Q

How can you differentiate between Streptococcus pyogenes and Streptococcus agalactiae on blood agar?

A

By testing its sensitivity to bacitracin (S pyogenes is sensitive and S agalactiae is resistant)

293
Q

How do you counsel a pregnant woman to prevent transmission of Listeria monocytogenes?

A

Avoid ingestion of unpasteurized dairy products and cold deli meats; L monocytogenes grows well at refrigeration temperatures

294
Q

Your ill patient’s blood cultures are now growing coagulase ⊖ Staphylococcus. What are the possible pathogens?

A

Staphylococcus saprophyticus or Staphylococcus epidermidis (coagulase ⊖ strains are common contaminants in blood cultures)

295
Q

Name the organisms of the viridans group streptococci and their associated diseases.

A

Streptococcus mutans and Streptococcus mitis cause dental caries, Streptococcus sanguinis causes subacute bacterial endocarditis

296
Q

What abnormalities may present in a case of congenital syphilis?

A

Saber shins, saddle nose, CN VIII deafness, Hutchinson (notched) teeth, mulberry molars, rhagades, snuffles, short maxilla

297
Q

Compare the T-cell responses associated with lepromatous versus tuberculoid leprosy.

A

Lepromatous form causes a Th2 response (Lepromatous is Lethal); tuberculoid form causes a Th1 response

298
Q

Pseudomonas aeruginosa exotoxin A shares a mechanism with which pseudomembrane-forming pathogen?

A

Pseudomonas aeruginosa’s exotoxin A and Corynebacterium diphtheriae’s diphtheria toxin both inhibit EF-2

299
Q

How does coagulase positivity contribute to the pathogenicity of Staphylococcus aureus?

A

It allows the organism to form a fibrin clot around itself, permitting abscess formation

300
Q

What are the various treatment options for Pseudomonas aeruginosa infection? (Hint: CAMPFIRE)

A

Carbapenems, Aminoglycosides, Monobactams, Polymyxins, Fluoroquinolones, thIRd/fourth-generation cephalosporins, Extended-spectrum penicillins

301
Q

What spirochete causes destruction of the vasa vasorum of the aorta?

A

Treponema pallidum, which causes tertiary syphilis (diagnosis: aortitis)

302
Q

What pyogenic illnesses are caused by Streptococcus pyogenes?

A

Pharyngitis, erysipelas, impetigo (“honey-crusted” lesions), cellulitis

303
Q

Which Chlamydia trachomatis serotypes cause lymphogranuloma venereum?

A

Types L1, L2, and L3

304
Q

The Haemophilus influenzae vaccine is typically given to which age group?

A

Infants 2-18 months of age

305
Q

What 2 features differentiate gonococcus from meningococcus?

A

Neisseria gonorrhoeae lacks polysaccharide capsule, produces acid via glucose; N meningitidis has a polysaccharide capsule and ferments maltose and glucose

306
Q

Name 3 possible scenarios that may give a ⊕ PPD test result.

A

Current tuberculosis infection, previous exposure to tuberculosis, and bacille Calmette-Guérin (BCG) vaccination

307
Q

How is the screening sample to test for group B streptococci collected in a pregnant woman?

A

Rectal and vaginal swabs

308
Q

What are the 2 different types of presentations with Bacillus cereus infection?

A

Emetic and diarrheal types

309
Q

Which bacteria can be identified as gram ⊖ diplococci?

A

Neisseria species and Moraxella species

310
Q

What Escherichia coli virulence factor is responsible for development of cystitis and pyelonephritis?

A

Fimbriae (P pili specifically for pyelonephritis)

311
Q

Dysarthria, dysphagia, and diplopia develop after a man eats food from a poorly sealed can. What is the mechanism of the causative toxin?

A

Inhibition of acetylcholine release at the neuromuscular junction, causing botulism (this heat-labile toxin is produced by Clostridium botulinum)

312
Q

A girl presents with a strawberry tongue, circumoral pallor, sore throat, fever, and sandpaper-like body rash. Causative agent?

A

Streptococcus pyogenes (diagnosis: scarlet fever caused by the erythrogenic toxin)

313
Q

What characteristic finding can you see while examining Listeria monocytogenes under the microscope in broth?

A

Tumbling motility

314
Q

What is the causative organism and vector of ehrlichiosis?

A

Ehrlichia chaffeensis, which is carried by the Lone Star tick (Amblyomma)

315
Q

Why might a bacterial infection in a patient with whooping cough be mistaken for a viral infection?

A

The immune response to Bordetella pertussis generates a lymphocytic infiltrate

316
Q

You culture 2 different α-hemolytic species. What might catalase and optochin sensitivity testing reveal?

A

Streptococcus pneumoniae is optochin sensitive, viridans streptococci are resistant; all are catalase ⊖

317
Q

In what stage of syphilis would a patient note lymphadenopathy and patchy hair loss?

A

Secondary syphilis

318
Q

What are the modes of transmission of Neisseria gonorrhoeae?

A

N gonorrhoeae is transmitted during sex or birth

319
Q

What novobiocin-sensitive bacterium found in normal skin flora commonly contaminates blood cultures?

A

Staphylococcus epidermidis

320
Q

In the lab, you observe a group of lactose-nonfermenting gram ⊖ bacilli that are also oxidase positive. Likely bacteria?

A

Pseudomonas

321
Q

What is the vector and the pathogen causing endemic typhus?

A

Fleas; transmit Rickettsia typhi

322
Q

In which host cell type do bacterial microcolonies form when a patient is infected with anaplasmosis?

A

Granulocytes; Monocytes for Ehrlichiosis; Granulocytes for Anaplasma (MEGA berry)

323
Q

A man has an ulcerating lesion with black eschar. A culture shows gram ⊕ spore-forming organisms. What are the organisms?

A

Bacillus anthracis (gram ⊕ spore-forming rods)

324
Q

How does Staphylococcus aureus infection cause toxic shock syndrome?

A

Toxic shock syndrome is caused by superantigen TSST-1 that binds MHC II and T-cell receptors, results in polyclonal T-cell activation and cytokine release

325
Q

How is neonatal Chlamydia acquired?

A

As the infant passes through an infected birth canal

326
Q

When α-hemolytic bacteria are grown on blood agar, a greenish-brownish color without peripheral clearing results in the colonies. What is responsible for this color?

A

Partial oxidation of hemoglobin

327
Q

What gram ⊖, aerobic coccobacillus resides in macrophages of the reticuloendothelial system and is transmitted via contaminated animal products?

A

Brucella

328
Q

Why do you confirm a positive Venereal Disease Research Laboratory (VDRL) result with a fluorescent treponemal antibody–absorbed (FTA-ABS) test when testing for syphilis?

A

An FTA-ABS test is more specific for syphilis; a VDRL test is more sensitive and more likely to yield a false-positive result

329
Q

A patient has severe diarrhea; exam reveals pseudomembranous colitis, and culture shows gram ⊕ spore-forming bacilli. Treatment?

A

Oral vancomycin, metronidazole, or fidaxomicin (this is infection with Clostridium difficile [Difficile causes diarrhea])

330
Q

How would a patient with Weil disease (icterohemorrhagic leptospirosis) present?

A

Jaundice and azotemia from liver and kidney dysfunction, fever, hemorrhage, and anemia (severe form of leptospirosis)

331
Q

How is tularemia contracted?

A

From rabbits, deer flies, and ticks containing Francisella tularensis

332
Q

A woman is 37 weeks pregnant with positive cultures for Streptococcus agalactiae. What medication should be used as prophylaxis?

A

Prophylactic intrapartum penicillin/ampicillin administration for Streptococcus agalactiae infection

333
Q

A patient comes in with food poisoning caused by Staphylococcus aureus despite eating properly cooked food. What is the reason for the illness?

A

Enterotoxin is heat stable and not destroyed by cooking

334
Q

In the lab, you have a coagulase ⊖ Staphylococcus bacterium. You notice that it is novobiocin sensitive. Identify it.

A

NOvobiocin: Saprophyticus is Resistant; Epidermidis is Sensitive (NO StRESs on the office “staph” retreat)

335
Q

Which gram ⊕ filamentous and weakly acid-fast bacteria spread to the CNS?

A

Nocardia

336
Q

Subacute endocarditis develops after a patient undergoes a cystoscopy. What is the likely causative organism?

A

Enterococci; patients are prone to such infections after gastrointestinal and genitourinary procedures

337
Q

What 3 possible colors do colonies of lactose-fermenting bacteria exhibit on EMB agar?

A

Purple and black; Escherichia coli grows with a green sheen

338
Q

Where do Pasteurella infections often originate from?

A

Various animals via bites, particularly dogs and cats

339
Q

Following severe bacteremia caused by tuberculosis, what might be seen on examination of histopathology slides from various organs?

A

Small, widespread granulomas in multiple organs; diagnosis: miliary tuberculosis

340
Q

In the lab, you discover an oxidase ⊕, comma-shaped, gram ⊖ bacterium that grows at 42°C. Identify this bacterium

A

Campylobacter jejuni

341
Q

What are the virulence factors produced by Pseudomonas aeruginosa?

A

Phospholipase C; Endotoxin; Exotoxin A; Pigments: pyoverdine and pyocyanin (PEEP)

342
Q

What medium is used to culture Haemophilus influenzae?

A

Chocolate agar with factors V (NAD+) and X (hematin); can also be grown with Staphylococcus aureus, which provides factor V by way of RBC hemolysis

343
Q

In the lab, you grow normal skin bacteria that are gram ⊕, catalase ⊕, coagulase ⊖, urease ⊕ cocci in clusters, sensitive to novobiocin. What organism was isolated?

A

Staphylococcus epidermidis

344
Q

Name 4 Clostridium species that produce exotoxins

A

Clostridium perfringens, C botulinum, C tetani, and C difficile

345
Q

What are the 2 virulence factors of Shigella species?

A

Endotoxin and Shiga toxin (enterotoxin)

346
Q

The mnemonic ABCDEFG is useful for remembering key information about Corynebacterium diphtheriae. Explain this mnemonic.

A

Adenosine diphosphate - (ADP) ribosylation; β-prophage; Corynebacterium Diphtheriae; Elongation Factor 2; Granules

347
Q

What are the laboratory characteristics of Vibrio cholerae?

A

Gram ⊖, comma-shaped, flagellated, oxidase ⊕ bacteria that grow in alkaline media and are acid-labile (sensitive to stomach acid)

348
Q

Which bacteria is a gram ⊕, filamentous, weakly acid-fast aerobe usually found in soil and mostly affects immunocompromised hosts?

A

Nocardia

349
Q

Which part of the body does Helicobacter pylori typically colonize?

A

Antrum of the stomach

350
Q

The Rickettsia genus bacteria are transmitted by way of what vector?

A

Arthropods (eg, ticks), except Coxiella, which is transmitted in aerosols

351
Q

Which bacteria grow pink colonies on MacConkey agar?

A

Escherichia coli, Enterobacter, and Klebsiella

352
Q

An unvaccinated boy has a “cherry red” epiglottis, and a lateral neck x-ray shows the “thumb sign.” What is the most likely causative agent?

A

Haemophilus influenzae

353
Q

In the lab, you identify a streptococcal species sensitive to bacitracin. Which strain is this?

A

Bacitracin: group B streptococci are Resistant; group A streptococci are Sensitive (B-BRAS)

354
Q

How is the bacteria Legionella pneumophila transmitted?

A

Aerosol transmission from an environmental water source such as an air conditioner or hot water tank (no person-to-person transmission)

355
Q

Which strain of Haemophilus influenzae most commonly causes the most invasive disease?

A

Nontypeable (unencapsulated) strains

356
Q

What kind of illnesses does Yersinia enterocolitica typically cause?

A

Acute bloody diarrhea, pseudoappendicitis, reactive arthritis (in adults)

357
Q

What product of Pseudomonas aeruginosa causes degradation of cell membranes?

A

Phospholipase C

358
Q

Describe the laboratory properties of Streptococcus pyogenes (group A streptococci).

A

Gram ⊕ cocci in chains, β-hemolytic, bacitracin sensitive, and pyrrolidonyl arylamidase (PYR) ⊕

359
Q

How is the Veneral Disease Research Laboratory (VDRL) test typically used in the work-up for syphilis?

A

As a screening test; VDRL is considered sensitive but not specific (being widely available, it is often used for initial screening)

360
Q

A sexually active patient develops a Gardnerella vaginalis infection, but her partner does not. What is the reason?

A

Gardnerella vaginalis is not sexually transmitted despite its association with sexual activity

361
Q

Bacterial colonies that grow pink on MacConkey agar have the ability to do what?

A

Ferment lactose

362
Q

Which β-hemolytic bacteria is a catalase-negative, bacitracin-resistant, gram-positive cocci?

A

Streptococcus agalactiae (group B strep)

363
Q

In the lab, gram ⊕ bacteria form a halo of projections like “medusa head” colonies. What is the capsule made of?

A

Bacillus anthracis synthesizes a polypeptide capsule (contains poly D-glutamate)

364
Q

What type of laboratory sample is tested to diagnose Legionella infection?

A

Urine is used to detect presence of antigen

365
Q

How is Coxiella burnetti, the causative organism behind Q fever, transmitted?

A

Via the aerosols of cattle and sheep amniotic fluid

366
Q

What percentage of patients with primary syphilis will be VDRL positive?

A

80%

367
Q

What 2 mycobacterial species are usually resistant to multiple drugs?

A

Mycobacterium tuberculosis and Mycobacterium avium–intracellulare

368
Q

What treatment is recommended in a patient with recurrent Clostridium difficile infections to prevent relapse?

A

Repeat courses of metronidazole, oral vancomycin, or fidaxomicin; for refractory cases, a fecal microbiota transplant can be performed

369
Q

Borrelia burgdorferi, which causes Lyme disease, relies on what animals in order to replicate and spread?

A

Mouse: serves as a natural reservoir; Ixodes deer tick: transmits Borrelia; deer: essential to tick life cycle but does not harbor Borrelia itself

370
Q

How does Enteroinvasive Escherichia coli (EIEC) cause dysentery?

A

EnteroInvasive E coli (EIEC) Invades the mucosa of the intestine, causing necrosis and inflammation leading to dysentery (clinically similar to Shigella)

371
Q

What organ does Salmonella typhi colonize?

A

Gallbladder

372
Q

What component of virulent Mycobacterium tuberculosis induces release of TNF-α?

A

Cord factor

373
Q

Why is drug sensitivity testing important when a patient has an infection caused by intestinal flora Klebsiella?

A

Klebsiella is associated with multidrug resistance

374
Q

In the microbiology lab, you identify a β-hemolytic organism that is both catalase and coagulase ⊕. What organism did you find?

A

Staphylococcus aureus

375
Q

What form of leprosy presents with diffuse, communicable skin lesions and leonine facies?

A

Lepromatous leprosy

376
Q

How does a streptococcal strain that shows complete hemolysis with a PYR ⊕ status react to bacitracin?

A

It is bacitracin sensitive; this is group A (Streptococcus pyogenes) beta-hemolytic streptococci

377
Q

What 2 pathologic conditions in the gastrointestinal tract are caused by Helicobacter pylori?

A

Gastritis and peptic ulcers (especially duodenal)

378
Q

What are the Gram stain characteristics of Legionella?

A

Legionella is a gram ⊖ bacillus but does not react well to Gram stain; use silver stain

379
Q

A man receives intramuscular penicillin for treatment of syphilis and later has fever, chills, headache, and myalgia. What caused these symptoms?

A

The Jarisch-Herxheimer reaction, a flu-like syndrome due to release of toxins by bacteria (usually spirochetes) killed by antibiotics

380
Q

What is the treatment for a patient infected with Brucella?

A

Doxycycline + rifampin or streptomycin

381
Q

Blood agar grows a β-hemolytic organism. How would you differentiate both Streptococcus pyogenes and Streptococcus agalactiae from Staphylococcus aureus?

A

Both are catalase ⊖, unlike S aureus, which is catalase ⊕

382
Q

What is the treatment of atypical pneumonia?

A

Macrolides, doxycycline, or flurorquinolones

383
Q

You find gram ⊕ bacilli in a specimen that are able to survive without oxygen. Which bacteria are they?

A

Cutibacterium (formerly known as Propionibacterium) and Clostridium

384
Q

What does the presence of constitutional symptoms in a patient with syphilis indicate?

A

Disseminated disease (as opposed to a localized infection as seen with chancre)

385
Q

Which disease is spread by parrots and other birds, and what is the pathogen?

A

Psittacosis; caused by Chlamydophila psittaci

386
Q

What are the common sources of infection for Pseudomonas aeruginosa?

A

Water from sources such as swimming pools and hot tubs (P aeruginosa causes swimmer’s ear and hot tub folliculitis)

387
Q

Name the toxins produced by Staphylococcus aureus and their associated effects.

A

TSST-1 causes toxic shock syndrome; exfoliative toxin causes scalded skin syndrome; enterotoxin causes rapid-onset food poisoning

388
Q

What symptoms characterize the first stage (early localized) of Lyme disease?

A

Erythema migrans (expanding red “bull’s-eye” rash) and flu-like symptoms

389
Q

Describe Helicobacter pylori’s morphology and Gram staining pattern.

A

Curved, flagellated (motile), gram ⊖ rod

390
Q

Which conditions can result in a false positive Venereal Disease Research Laboratory (VDRL) test?

A

Pregnancy, viral infection (EBV, hepatitis), drugs (chlorpromazine, procainamide), rheumatic fever (rare), lupus or leprosy

391
Q

What type of Pseudomonas toxin produces symptoms of sepsis?

A

Endotoxin

392
Q

What is the Gram stain reaction and shape of Bordetella pertussis?

A

Gram ⊖ coccobacillus

393
Q

How do antibiotics affect fecal excretion of Salmonella vs Shigella?

A

How do antibiotics affect fecal excretion of Salmonella vs Shigella? Antibiotics prolong the duration of fecal excretion of Salmonella while shortening duration of fecal excretion of Shigella

394
Q

What prophylaxis should be offered to a health care worker who may have been exposed to Neisseria meningitidis?

A

Rifampin, ciprofloxacin, or ceftriaxone

395
Q

In patients with Chlamydia infection, why is azithromycin the favored treatment?

A

It is a one-time treatment (in contrast to doxycycline, which requires several doses)

396
Q

In the lab, you identify a streptococcal species resistant to bacitracin. Which strain is this?

A

Bacitracin: group B streptococci are Resistant; group A streptococci are Sensitive (B-BRAS)

397
Q

What is the classic triad of symptoms of Rocky Mountain spotted fever?

A

Fever, headache, and rash (vasculitis)

398
Q

When does neonatal conjunctivitis caused by Chlamydia present?

A

1-2 weeks after birth

399
Q

What organism is the second most common cause of uncomplicated urinary tract infection (UTI) in young women?

A

Staphylococcus saprophyticus

400
Q

Why is a patient at higher risk for Vibrio cholerae infection at low inoculum if they are under PPI therapy when visiting a developing country?

A

PPIs ↓ gastric acidity; V cholerae typically requires a large inoculum (ID50) because it is sensitive to stomach acid

401
Q

What 3 strains of Escherichia coli do not invade the intestinal mucosa?

A

Enterotoxigenic (ETEC), enteropathogenic (EPEC), and enterohemorrhagic (EHEC); only the enteroinvasive (EIEC) strain invades intestinal mucosa

402
Q

Which 2 Chlamydiae species are transmitted by aerosol and cause atypical pneumonia?

A

Chlamydophila pneumoniae and Chlamydophila psittaci

403
Q

Name 7 common sites of extrapulmonary tuberculosis.

A

Vertebrae (Pott disease), meninges, lymph nodes, liver, spleen, adrenal glands, joints/long bones

404
Q

Which 3 bacteria are fast lactose-fermenting gram ⊖ bacilli?

A

Klebsiella, Escherichia coli, and Enterobacter

405
Q

A patient with Helicobacter pylori has an ↑ risk for which 2 cancers?

A

Gastric adenocarcinoma and mucosa-associated lymphoid tissue (MALT) lymphoma

406
Q

A louse is a vector for which bacterial species?

A

Borrelia recurrentis

407
Q

An aerobic catalase ⊖ culture of cocci in chains exhibits complete hemolysis. How will you further categorize the species?

A

These are streptococci exhibiting β-hemolysis: Streptococcus pyogenes is bacitracin sensitive and PYR ⊕ while Streptococcus agalactiae is bacitracin resistant and PYR ⊖

408
Q

A 35-year-old man complains of pain and swelling along the inguinal lymph nodes, which have begun to ulcerate, forming buboes. What is the treatment?

A

Treat with doxycycline (Chlamydia trachomatis types L1, L2, and L3 cause Lymphogranuloma venereum)

409
Q

Describe how food poisoning can arise from food contaminated with Clostridium perfringens spores.

A

Spores germinate when food is left standing at <60°C, giving rise to vegetative bacteria that produces heat-labile enterotoxin, causing food poisoning symptoms

410
Q

A boy who ate food from a poorly sealed container comes to the office with diplopia and ↓ tone in his arms. Diagnosis?

A

Clostridium botulinum

411
Q

How is Vibrio cholerae transmitted?

A

By consumption of contaminated water or uncooked food (eg, raw shellfish)

412
Q

What 2 immediate complications are possible if a patient contracts an infection with Streptococcus bovis?

A

Bacteremia and subacute endocarditis

413
Q

Do Salmonella and Shigella both have flagella?

A

Salmonella contain flagella (enabling hematogenous dissemination); Shigella do not

414
Q

What is the Gram stain and morphology of Yersinia enterocolitica?

A

Gram ⊖ pleomorphic rod/coccobacillus

415
Q

What features help in isolating Streptococcus pneumoniae from a culture medium?

A

They are gram ⊕, α-hemolytic, lancet-shaped diplococci, which are sensitive to optochin and bile soluble

416
Q

Which organism may be either α-hemolytic or γ-hemolytic?

A

Enterococcus

417
Q

What do patients with Salmonella and Shigella have in common with their clinical presentation?

A

Both Salmonella and Shigella often cause bloody diarrhea (note that S typhi diarrhea is often preceded by constipation)

418
Q

A woman who complains of pain in the right lower quadrant and cervical motion tenderness has a blood smear (image) showing gram ⊖ intracellular diplococci. Diagnosis?

A

Pelvic inflammatory disease (PID) due to Neisseria gonorrhoeae infection (image shows diplococci within a neutrophil)

419
Q

The Ixodes deer tick is a vector for which 3 pathogens?

A

Borrelia burgdorferi, Anaplasma, and Babesia

420
Q

What do the red and black arrows in this patient with congenital syphilis indicate?

A

Black arrow: rhagades (linear scars at angle of mouth); red arrow: snuffles (nasal discharge)

421
Q

A boy presents with abnormal facies (image). How communicable is this form of disease?

A

Highly communicable; this is the lepromatous form of leprosy; it presents with a high bacterial load and low cell-mediated immunity

422
Q

How would you describe the morphology of Mycoplasma?

A

Pleomorphic

423
Q

A culture on blood agar from a 70-year-old man with productive cough grows a bacterial species shown (image). What is the causative organism?

A

Streptococcus pneumoniae (α-hemolysis)

424
Q

What is the treatment of choice for a patient with acute hypotension, petechiae, and toe gangrene (see image) that develop in the setting of meningococcemia?

A

Ceftriaxone or penicillin G (diagnosis: Waterhouse-Friderichsen syndrome, caused by meningococci)

425
Q

The gram ⊕ rod in the image resembles fungi and responds best to sulfonamides. What is it?

A

Nocardia

426
Q

What is used to visualize treponemes in primary syphilis?

A

Fluorescent or dark-field microscopy

427
Q

A biopsy of a cavitary lesion found in the chest x-ray of a patient with chronic cough is shown in the image. Diagnosis?

A

Secondary tuberculosis; biopsy shows a caseating granuloma with central necrosis and a Langhans giant cell (image)

428
Q

On ocular exam, a patient has the findings shown in the image. Diagnosis?

A

Follicular adult conjunctivitis, caused by Chlamydiae trachomatis

429
Q

A man has fever, diarrhea, and headache. A CT of the chest is shown (image). Initial lab test shows hyponatremia. The sputum culture Gram stains poorly. Diagnosis?

A

Likely Legionnaires’ disease; note the unilateral and lobar pneumonia

430
Q

What gives the mucoid appearance of Klebsiella pneumoniae colonies?

A

Polysaccharide capsules

431
Q

The gram ⊕ rod in the image forms long, branching filaments resembling fungi and responds well to penicillin. What is it?

A

Actinomyces

432
Q

A 25-year-old woman presents with vaginal discharge; microscopy findings are shown (image). Treatment?

A

Metronidazole or clindamycin (image shows a clue cell from Gardnerella vaginalis infection)

433
Q

The bacteria shown in the image are gram ⊕, α-hemolytic, lancet-shaped diplococci. They are isolated from a patient’s sputum sample. What color is the sputum expected to be?

A

Rusty-colored sputum (the likely organism is Streptococcus pneumoniae)

434
Q

You observe the findings in the image on blood agar from gram-positive cocci. The bacterium is bacitracin resistant. What is it?

A

Streptococcus agalactiae

435
Q

The image shows an organism isolated from a patient with a wound infection showing irregular margins of erythema and swelling. Diagnosis?

A

Cellulitis (image shows gram ⊕ cocci arranged in chains indicating Streptococcus pyogenes)

436
Q

What are some cutaneous manifestations of secondary syphilis, including the finding shown in the image?

A

Condylomata lata (smooth, painless, wart-like lesions on genitalia), maculopapular rash (including palms and soles), patchy hair loss

437
Q

The image shows a granulocyte infected with a rickettsial disease. What finding is indicated by the arrow?

A

Berry-like inclusions called morulae (arrow in the image) in the cytoplasm (when infected with Anaplasma)

438
Q

A patient has the colonoscopic findings shown (image). Which 2 antibiotics most likely could be secondary causes of the patient’s presentation?

A

Clindamycin and ampicillin (this is infection with Clostridium difficile)

439
Q

What is the mechanism leading to profuse rice-water diarrhea caused by an infection with bacteria seen in the image?

A

Via enterotoxin, which permanently activates Gs → ↑ cAMP (diagnosis: Vibrio cholerae)

440
Q

What treatment can be offered to a woman who has multiple sexual partners and presents with a new rash on her palms and abdomen (image)?

A

Penicillin G (used to treat all stages of syphilis)

441
Q

An immunocompromised patient has a rapidly progressing necrotic skin lesion (image) that grows a blue-green pigment-producing organism when cultured. Diagnosis?

A

Ecthyma gangrenosum, caused by Pseudomonas aeruginosa (seen mostly in immunocompromised states)

442
Q

An image of a new patient is shown. What other signs should you be concerned about because of the likely causative organism?

A

Diagnosis: tertiary syphilis gummas (chronic granulomas); other signs: broad-based ataxia, Romberg sign ⊕, Charcot joint, and strokes without hypertension

443
Q

What 2 pigments are produced by Pseudomonas aeruginosa to give it the appearance shown here?

A

Pyoverdine and pyocyanin (blue-green pigment, also generate reactive oxygen species)

444
Q

A 4-year-old boy is febrile, lethargic, stridulous, and drooling. His epiglottis is shown (image). What vaccine could have prevented this?

A

Haemophilus influenzae type b vaccine (the patient likely has epiglottitis)

445
Q

How could infection have been prevented in a child who presents with the findings shown in the image, as well as with saddle nose and saber shins?

A

Treat mother with penicillin early in pregnancy because placental transmission of syphilis usually occurs after first trimester (image shows Hutchinson teeth)

446
Q

An adolescent boy presents with a gunshot wound to the leg. Physical exam reveals soft tissue crepitus and lesions as shown (image). What is the mechanism of the toxin?

A

An alpha-toxin (lecithinase, a phospholipase) produced by Clostridium perfringens can cause myonecrosis (gas gangrene presenting as soft tissue crepitus) and hemolysis

447
Q

What stage of syphilis presents with the finding in the image?

A

Primary syphilis (image is a painless chancre)

448
Q

What process results in the hemolysis pattern shown in the image?

A

Complete lysis of red blood cells; on blood agar → pale/clear area surrounding colonies

449
Q

What are spirochetes?

A

Spiral-shaped bacteria with axial filaments

450
Q

A patient has the finding shown (image). Work-up reveals metachromatic (blue and red) granules and a positive Elek test. Name the organism.

A

Corynebacterium diphtheriae

451
Q

A patient presents with cough and night sweats. Sputum staining is shown in the image. Diagnosis?

A

Pulmonary tuberculosis (arrow points to pink rods, indicating acid-fast bacilli)

452
Q

Infection with what bacteria leads to a “glove and stocking” loss of sensation?

A

Mycobacterium leprae likes cool temperatures and therefore affects the skin and superficial nerves

453
Q

A man is bitten by a tick and has no rash. Results of a blood smear are shown in the image. Diagnosis?

A

Ehrlichiosis, characterized by the presence of morulae in monocytes (morulae are cytoplasmic inclusions resembling berries)

454
Q

A hiker in the northeastern United States discovers a rash on his arm (image). An ECG shows an AV block pattern. What medications are used in the treatment?

A

Doxycycline (first line); amoxicillin, and ceftriaxone for severe illness, CNS signs, or heart block (this is secondary Lyme disease)

455
Q

A patient is found to have thickening of his epiglottis (image) caused by infection with small, gram ⊖ coccobacillary rods. Treatment?

A

Amoxicillin +/– clavulanate for mucosal infections (image is the thumbprint sign, seen in Haemophilus influenzae epiglottitis)

456
Q

If a pregnant woman is infected with this facultative intracellular microbe acquired from cold deli meats (see image), what complications before and after delivery could arise?

A

Before delivery: amnionitis, septicemia, spontaneous abortion
After delivery: granulomatosis infantiseptica, neonatal meningitis
(this is Listeria)

457
Q

A shepherd has a skin lesion with a painless papule surrounded by vesicles as shown in the image. What is the organism?

A

Bacillus anthracis (gram ⊕ spore-forming rods)

458
Q

Gram-positive, catalase-positive, coagulase-positive cocci in clusters are shown in the image. What type of hemolysis is seen on blood agar?

A

Image shows Staphylococcus aureus, which is β-hemolytic

459
Q

You observe the findings in the image on blood agar from gram-positive cocci. Name 3 bacterial strains that can cause this.

A

Staphylococcus aureus, Streptococcus pyogenes, Streptococcus agalactiae (these are all β-hemolytic bacteria)