Microbiology - Clinical Bacteriology Flashcards
1
Q
Gram-positive lab algorithm (129)
A
2
Q
Identification of gram-positive cocci
- Staphylococci
- Streptococci
A
- Staphylococci
-
NOvobiocin
- _S_aprophyticus is _R_esistant;
- _E_pidermidis is _S_ensitive.
- On the office’s “staph” retreat, there was NO St_RES_s.
-
NOvobiocin
- Streptococci
-
Optochin
- _V_iridans is _R_esistant;
- _P_neumoniae is _S_ensitive.
- OVRPS (overpass).
-
Bacitracin
- Group B** strep are **Resistant;
- Group A** strep are **Sensitive.
- B-BRAS.
-
Optochin
3
Q
α- vs. β-hemolytic bacteria
- α-hemolytic bacteria
- β-hemolytic bacteria
A
- α-hemolytic bacteria
- Form green ring around colonies on blood agar.
- Include the following organisms:
- Streptococcus pneumoniae (catalase (-) and optochin sensitive)
- Viridans streptococci (catalase (-) and optochin resistant)
- β-hemolytic bacteria
- Form clear area of hemolysis on blood agar.
- Include the following organisms:
- Staphylococcus aureus (catalase and coagulase (+))
- Streptococcus pyogenes—group A strep (catalase (-) and bacitracin sensitive)
- Streptococcus agalactiae—group B strep (catalase (-) and bacitracin resistant)
- Listeria monocytogenes (tumbling motility, meningitis in newborns, unpasteurized milk)
4
Q
Staphylococcus aureus
- Properties
- Causes…
- TSST
- S. aureus food poisoning
A
- Properties
- Gram-positive cocci in clusters [A].
- Protein A (virulence factor) binds Fc-IgG, inhibiting complement activation and phagocytosis.
- Commonly colonizes the nose.
- Staph make catalase because they have more “staff.”
- Bad staph (aureus) make coagulase and toxins.
- Causes…
-
Inflammatory disease—skin infections, organ abscesses, pneumonia (often after influenza virus infection), endocarditis, and osteomyelitis
- Forms fibrin clot around self –> abscess.
- Toxin-mediated disease—toxic shock syndrome (TSST-1), scalded skin syndrome (exfoliative toxin), rapid-onset food poisoning (enterotoxins)
- MRSA (methicillin-resistant S. aureus) infection—important cause of serious nosocomial and community-acquired infections; resistant to methicillin and nafcillin because of altered penicillin-binding protein
-
Inflammatory disease—skin infections, organ abscesses, pneumonia (often after influenza virus infection), endocarditis, and osteomyelitis
- TSST
- A superantigen that binds to MHC II and T-cell receptor, resulting in polyclonal T-cell activation.
- Presents as fever, vomiting, rash, desquamation, shock, end-organ failure.
- Use of vaginal or nasal tampons predisposes to toxic shock syndrome.
- S. aureus food poisoning
- Due to ingestion of preformed toxin –> short incubation period (2–6 hr).
- Enterotoxin is heat stable –> not destroyed by cooking.
5
Q
Staphylococcus
- Staphylococcus epidermidis
- Staphylococcus saprophyticus
A
- Staphylococcus epidermidis
- Infects prosthetic devices and intravenous catheters by producing adherent biofilms.
- Component of normal skin flora
- Contaminates blood cultures.
- Novobiocin sensitive.
- Staphylococcus saprophyticus
- Second most common cause of uncomplicated UTI in young women (first is E. coli).
- Novobiocin resistant.
6
Q
Streptococcus pneumoniae
- Most common cause of…
- Properties
- Pneumococcus is associated with…
- Virulence
A
- Most common cause of…
- Meningitis
- Otitis media (in children)
- Pneumonia
- Sinusitis
- S. pneumoniae MOPS are Most OPtochin Sensitive
- Properties
- Lancet-shaped, gram-positive diplococci [A].
- Encapsulated.
- IgA protease.
- No virulence without capsule.
- Pneumococcus is associated with “rusty” sputum, sepsis in sickle cell anemia and splenectomy.
7
Q
Viridans group streptococci
- Properties
- Cause…
- S. sanguinis
A
- Properties
- Viridans streptococci are α-hemolytic.
- Normal flora of the oropharynx
- Resistant to optochin, differentiating them from S. pneumoniae, which is α-hemolytic but is optochin sensitive.
- Viridans group strep live in the mouth because they are not afraid of-the-chin (op-to-chin resistant)
- Cause
- Dental caries (Streptococcus mutans)
- Subacute bacterial endocarditis at damaged valves (S. sanguinis)
- S. sanguinis
- Sanguis = blood.
- There is lots of blood in the heart (endocarditis).
- S. sanguinis makes dextrans, which bind to fibrin-platelet aggregates on damaged heart valves.
8
Q
Streptococcus pyogenes (group A streptococci)
- Causes…
- Properties
- Jones criteria
A
- Causes…
- Pyogenic—pharyngitis, cellulitis, impetigo
- Impetigo more commonly precedes glomerulonephritis than pharyngitis.
- Toxigenic—scarlet fever, toxic shock–like syndrome, necrotizing fasciitis
- Scarlet fever: scarlet rash with sandpaper-like texture, strawberry tongue, circumoral pallor.
- Immunologic—rheumatic fever, acute glomerulonephritis
- Pharyngitis can result in rheumatic “phever” and glomerulonephritis.
- Pyogenic—pharyngitis, cellulitis, impetigo
- Properties
- Bacitracin sensitive.
- Antibodies to M protein enhance host defenses against S. pyogenes but can give rise to rheumatic fever.
- ASO titer detects recent S. pyogenes infection.
-
J♥NES criteria for rheumatic fever
- Joints—polyarthritis
- ♥—carditis
- Nodules (subcutaneous)
- Erythema marginatum
- Sydenham chorea
9
Q
Streptococcus agalactiae (group B streptococci)
- Properties
- Causes…
- Produces…
- Screening
A
- Properties
- Bacitracin resistant
- β-hemolytic
- Colonizes vagina
- Causes…
- Pneumonia, meningitis, and sepsis, mainly in babies.
- Group **B for **Babies.
- Produces CAMP factor, which enlarges the area of hemolysis formed by S. aureus.
- Note: CAMP stands for the authors of the test, not cyclic AMP.
- Hippurate test (+).
- Screening
- Screen pregnant women at 35–37 weeks.
- Patients with (+) culture receive intrapartum penicillin prophylaxis.
10
Q
Group D streptococci
- Enterococci
- Definition
- Properties
- Streptococcus bovis
A
- Enterococci
- Definition
- Entero = intestine, faecalis = feces, strepto = twisted (chains), coccus = berry.
- Enterococci (Enterococcus faecalis and E. faecium) are normal colonic flora that are penicillin G resistant and cause UTI, biliary tract infections, and subacute endocarditis (following GI/GU procedures).
- Lancefield group D includes the enterococci and the nonenterococcal group D streptococci.
- Lancefield grouping is based on differences in the C carbohydrate on the bacterial cell wall.
- Properties
- Variable hemolysis.
- VRE (vancomycin-resistant enterococci) are an important cause of nosocomial infection.
- Enterococci, hardier than nonenterococcal group D, can grow in 6.5% NaCl and bile (lab test).
- Definition
- Streptococcus bovis
- Colonizes the gut.
- Can cause bacteremia and subacute endocarditis in colon cancer patients.
- Bovis in the blood = cancer in the colon.
11
Q
Corynebacterium diphtheriae
- Causes…
- Mechanism
- Symptoms
- Lab diagnosis
- Prevention
- Mnemonic
A
- Causes…
- Diphtheria via exotoxin encoded by β-prophage.
- Mechanism
- Potent exotoxin inhibits protein synthesis via ADP-ribosylation of EF-2.
- Symptoms
- Pseudomembranous pharyngitis (grayish-white membrane [A]) with lymphadenopathy, myocarditis, and arrhythmias.
- Lab diagnosis
- Based on gram-positive rods with metachromatic (blue and red) granules and Elek test for toxin.
- Black colonies on cystine-tellurite agar.
- Coryne = club shaped.
- Prevention
- Toxoid vaccine prevents diphtheria.
-
ABCDEFG:
- ADP-ribosylation
- Beta-prophage
- Corynebacterium
- Diphtheriae
- _E_longation _F_actor 2
- Granules
12
Q
Spores: bacterial
- Spores
- Spore-forming gram-positive bacteria found in soil
- Other spore formers
A
- Spores
- Some bacteria can form spores at the end of the stationary phase when nutrients are limited.
- Spores are highly resistant to heat and chemicals.
- Have dipicolinic acid in their core.
- Have no metabolic activity.
- Must autoclave to kill spores (as is done to surgical equipment) by steaming at 121°C for 15 minutes.
- Spore-forming gram-positive bacteria found in soil
- Bacillus anthracis, Clostridium perfringens, C. tetani.
- Other spore formers
- B. cereus, C. botulinum, Coxiella burnetii.
13
Q
Clostridia (with exotoxins)
- Clostridia
- C. tetani
- C. botulinum
- C. perfringens
- C. difficile
A
- Clostridia
- Gram-positive, spore-forming, obligate anaerobic bacilli.
- C. tetani
- Produces tetanospasmin, an exotoxin causing tetanus.
- Tetanus toxin (and botulinum toxin) are proteases that cleave releasing proteins for neurotransmitters.
-
Tetanus is tetanic paralysis
- Blocks glycine and GABA release (both are inhibitory neurotransmitters) from Renshaw cells in spinal cord
- Causes spastic paralysis, trismus (lockjaw), and risus sardonicus.
- Produces tetanospasmin, an exotoxin causing tetanus.
- C. botulinum
- Produces a preformed, heat-labile toxin that inhibits ACh release at the neuromuscular junction, causing botulism.
- In adults, disease is caused by ingestion of preformed toxin.
- In babies, ingestion of spores in honey causes disease (floppy baby syndrome).
- Botulinum is from bad bottles of food and honey (causes a flaccid paralysis).
- Produces a preformed, heat-labile toxin that inhibits ACh release at the neuromuscular junction, causing botulism.
- C. perfringens
- Produces α toxin (“lecithinase,” a phospholipase) that can cause myonecrosis (gas gangrene) and hemolysis.
- Perfringens perforates a gangrenous leg.
- C. difficile
- Produces 2 toxins.
- Toxin A, enterotoxin, binds to the brush border of the gut.
- Toxin B, cytotoxin, causes cytoskeletal disruption via actin depolymerization –> pseudomembranous colitis –> diarrhea.
- Difficile causes diarrhea.
- Often 2° to antibiotic use, especially clindamycin or ampicillin.
- Diagnosed by detection of one or both toxins in stool.
- Treatment: metronidazole or oral vancomycin.
- For recurring cases, fecal transplant may prevent relapse.
- Produces 2 toxins.
14
Q
Anthrax
- Caused by…
- Cutaneous anthrax
- Pulmonary anthrax
A
- Caused by Bacillus anthracis
- A gram-positive, spore-forming rod [A] that produces anthrax toxin.
- The only bacterium with a polypeptide capsule (contains D-glutamate).
- Cutaneous anthrax
- Boil-like lesion –> ulcer with black eschar [A] (painless, necrotic) –> uncommonly progresses to bacteremia and death.
- Pulmonary anthrax
- Inhalation of spores –> flu-like symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinitis, and shock.
- Woolsorters’ disease—inhalation of spores from contaminated wool.
15
Q
Bacillus cereus
- Causes…
- Emetic type
- Diarrheal type
A
- Causes food poisoning.
- Spores survive cooking rice.
- Reheated rice syndrome.
- Keeping rice warm results in germination of spores and enterotoxin formation.
- Spores survive cooking rice.
- Emetic type usually seen with rice and pasta.
- Nausea and vomiting within 1–5 hr.
- Caused by cereulide, a preformed toxin.
- Diarrheal type causes watery, nonbloody diarrhea and GI pain within 8–18 hr.
16
Q
Listeria monocytogenes
- Properties
- Causes…
- Treatment
A
- Properties
- Facultative intracellular microbe
- Acquired by ingestion of unpasteurized dairy products and deli meats, via transplacental transmission, or by vaginal transmission during birth.
- Form “rocket tails” (via actin polymerization) that allow them to move through the cytoplasm and into the cell membrane, thereby avoiding antibody.
- Characteristic tumbling motility
- Only gram-positive organism to produce LPS.
- Causes…
- Amnionitis, septicemia, and spontaneous abortion in pregnant women;
- Granulomatosis infantiseptica;
- Neonatal meningitis;
- Meningitis in immunocompromised patients;
- Mild gastroenteritis in healthy individuals.
- Treatment:
- Gastroenteritis usually self-limited
- Ampicillin in infants, immunocompromised patients, and the elderly in empirical treatment of meningitis.
17
Q
Actinomyces vs. Nocardia
- Both
- Gram
- Acid fast?
- Found in…
- Causes…
- Treatment
A
- Both
- Form long, branching filaments resembling fungi.
- Gram
- A: Gram-positive anaerobe [A]
- N: Gram-positive aerobe
- Acid fast?
- A: Not acid fast
- N: Acid fast (weak) [B]
- Found in…
- A: Normal oral flora
- N: Soil
- Causes…
- A: oral/facial abscesses that drain through sinus tracts, forms yellow “sulfur granules”
- N: pulmonary infections in immunocompromised and cutaneous infections after trauma in immunocompetent
- Treatment
- A: Penicillin
- N: Sulfonamides
18
Q
1° and 2° tuberculosis (134)
- PPD(+)
- PPD(-)
- Interferon-γ release assay (IGRA)
A
- PPD(+)
- If current infection, past exposure, or BCG vaccinated.
- PPD(-) i
- If no infection or anergic (steroids, malnutrition, immunocompromise) and in sarcoidosis.
- Interferon-γ release assay (IGRA)
- A more specific test
- Has fewer false positives from BCG vaccination.
19
Q
Mycobacteria
- M. tuberculosis
- M. kansasii
- M. avium
- All mycobacteria
- TB symptoms
- Cord factor
- Sulfatides
A
- M. tuberculosis
- TB, often resistant to multiple drugs
- M. kansasii
- Pulmonary TB-like symptoms
- M. avium–intracellulare
- Causes disseminated, non-TB disease in AIDS
- Often resistant to multiple drugs
- Prophylactic treatment with azithromycin.
- All mycobacteria are acid-fast organisms [A]
- TB symptoms
- Fever, night sweats, weight loss, and hemoptysis.
- Cord factor in virulent strains
- Inhibits macrophage maturation
- Induces release of TNF-α.
- Sulfatides (surface glycolipids)
- Inhibit phagolysosomal fusion.
20
Q
Leprosy (Hansen disease)
- Caused by…
- 2 forms
- Lepromatous
- Tuberculoid
- Treatment
- Lepromatous
- Tuberculoid
A
- Caused by Mycobacterium leprae
- An acid-fast bacillus
- Likes cool temperatures
- Infects skin and superficial nerves—“glove and stocking” loss of sensation
- Cannot be grown in vitro.
- Reservoir in United States: armadillos.
- 2 forms
-
Lepromatous
- Presents diffusely over the skin [A], with leonine (lion-like) facies [B], and is communicable
- Characterized by low cell-mediated immunity with a humoral Th2 response.
- Lepromatous can be lethal.
-
Tuberculoid
- Limited to a few hypoesthetic, hairless skin plaques
- Characterized by high cell-mediated immunity with a largely Th1- type immune response.
-
Lepromatous
- Treatment:
- Lepromatous
- Dapsone, rifampin, and clofazimine for 2–5 years
- Tuberculoid
- Multidrug therapy consisting of dapsone and rifampin for 6 months
- Lepromatous
21
Q
Gram-negative lab algorithm (136)
A
24
Q
Neisseria
- Neisseria
- Gonocci vs. Meningococci
- Polysaccharide capsule?
- Fermentation
- Vaccine?
- Transmission
- Causes…
- Prevention
- Treatment
A
- Neisseria
- Gram-negative diplococci
- Ferment glucose
- Produce IgA proteases
- N. gonorrhoeae is often intracellular (within neutrophils) [A]
-
Gonocci vs. Meningococci
- Polysaccharide capsule?
- G: No
- M: Yes
- Fermentation
- G: Gonococci ferment Glucose
- M: MeninGococci ferment Maltose and Glucose
- Vaccine?
- G: No (due to rapid antigenic variation of pilus proteins)
- M: Yes (none for type B)
- Transmission
- G: Sexually transmitted
- M: Respiratory and oral secretions
- Causes…
- G: Gonorrhea, septic arthritis, neonatal (PID), and Fitz-Hugh–Curtis syndrome
- M: Meningococcemia [B] and meningitis, Waterhouse-Friderichsen syndrome
- Prevention
- G: Condoms prevent sexual transmission; erythromycin ointment prevents neonatal transmission
- M: Rifampin, ciprofloxacin, or ceftriaxone prophylaxis in close contacts
- Treatment
- G: Ceftriaxone + (azithromycin or doxycycline) for possible chlamydia coinfection
- M: Ceftriaxone or penicillin G
- Polysaccharide capsule?
25
Q
Haemophilus influenzae
- Properties
- Culture
- Causes…
- Treatment
- Mucosal infections
- Meningitis
- Prophylaxis
A
- Properties
- Small gram-negative (coccobacillary) rod.
- Aerosol transmission.
- Most invasive disease caused by capsular type B.
- Nontypeable strains cause mucosal infections (otitis media, conjunctivitis, bronchitis).
- Produces IgA protease.
- Culture
- Culture on chocolate agar requires factors V (NAD+) and X (hematin) for growth
- Can also be grown with S. aureus, which provides factor V.
- When a child has “flu,” mom goes to five (V) and dime (X) store to buy some chocolate.
- Culture on chocolate agar requires factors V (NAD+) and X (hematin) for growth
- HaEMOPhilus causes…
- Epiglottitis [A] [B] (“cherry red” in children), Meningitis, Otitis media, and Pneumonia.
- Does not cause the flu (influenza virus does).
- Treatment
- Treat mucosal infections with amoxicillin +/- clavulanate.
- Treat meningitis with ceftriaxone.
- Prophylaxis
- Rifampin prophylaxis in close contacts.
- Vaccine contains type B capsular polysaccharide (polyribosylribitol phosphate) conjugated to diphtheria toxoid or other protein.
- Given between 2 and 18 months of age.
27
Q
Pseudomonas aeruginosa
- Properties
- Associated with…
- Ecthyma gangrenosum
- Treatment
A
- Properties
- Aerobic gram-negative rod.
- Non-lactose fermenting, oxidase (+).
- Produces pyocyanin (blue-green pigment [A]).
- Has a grape-like odor.
- Water source.
- Produces endotoxin (fever, shock) and exotoxin A (inactivates EF-2).
-
Aeruginosa—aerobic.
- Think water connection and blue-green pigment.
-
PSEUDOmonas is associated with…
- Wound and burn infections, Pneumonia (especially in cystic fibrosis), Sepsis, External otitis (swimmer’s ear), UTI, Drug use and Diabetic Osteomyelitis, and hot tub folliculitis.
- Think Pseudomonas in burn victims.
- Malignant otitis externa in diabetics.
- Chronic pneumonia in cystic fibrosis patients is associated with biofilm
- Wound and burn infections, Pneumonia (especially in cystic fibrosis), Sepsis, External otitis (swimmer’s ear), UTI, Drug use and Diabetic Osteomyelitis, and hot tub folliculitis.
-
Ecthyma gangrenosum
- Rapidly progressive, necrotic cutaneous lesions caused by Pseudomonas bacteremia.
- Typically seen in immunocompromised patients.
- Treatment
- Aminoglycoside plus extended-spectrum penicillin (e.g., piperacillin, ticarcillin, cefepime, imipenem, meropenem).
35
Q
Helicobacter pylori
- Causes…
- Properties
- Diagnosis
- Creates…
- Treatment
A
- Causes…
- Causes gastritis and peptic ulcers (especially duodenal).
- Risk factor for peptic ulcer, gastric adenocarcinoma and lymphoma.
- Creates alkaline environment.
- Properties
- Curved gram-negative rod
- Catalase, oxidase, and urease (+)
- Diagnosis
- Can use urea breath test or fecal antigen test for diagnosis.
- Treatment
- Most common initial treatment is triple therapy: proton pump inhibitor + clarithromycin + either amoxicillin or metronidazole.
36
Q
Spirochetes
- Properties
- Diagnosis
A
- Properties
- The spirochetes are spiral-shaped bacteria with axial filaments and include Borrelia (big size), Leptospira, and Treponema.
- BLT.
- B is Big.
- Diagnosis
- Only Borrelia can be visualized using aniline dyes (Wright or Giemsa stain) in light microscopy.
- Treponema is visualized by dark-field microscopy.
38
Q
Lyme disease
- Caused by…
- Reservoir
- Found…
- Symptoms
- Treatment
A
- Caused by…
- Borrelia burgdorferi, which is transmitted by the tick Ixodes [A] (also vector for Babesia).
- Reservoir
- Natural reservoir is the mouse.
- Mice are important to tick life cycle.
- Found…
- Common in northeastern United States.
- Symptoms
- Initial symptoms—erythema chronicum migrans [B], flu-like symptoms, +/- facial nerve palsy.
- Later symptoms—monoarthritis (large joints) and migratory polyarthritis, cardiac (AV nodal block), neurologic (encephalopathy, facial nerve palsy, polyneuropathy).
-
FAKE a Key Lyme pie:
- Facial nerve palsy (typically bilateral)
- Arthritis
- Kardiac block
- Erythema migrans
- Treatment
- Doxycycline, ceftriaxone.
39
Q
Syphilis
- Caused by…
- Treamtent
- 1° syphilis
- 2° syphilis
- 3° syphilis
- Congenital syphilis
A
- Caused by…
- Spirochete Treponema pallidum.
- Treatment
- Penicillin G.
- 1° syphilis
- Localized disease presenting with painless chancre [A].
- If available, use dark-field microscopy to visualize treponemes in fluid from chancre [B].
- Serologic testing: VDRL/RPR (non-specifc), confirm diagnosis with specific test (e.g., FTA-ABS).
- 2° syphilis
- Disseminated disease with constitutional symptoms, maculopapular rash (palms and soles), condylomata lata (also confirmable with dark-field microscopy).
- Secondary syphilis = Systemic
- Serologic testing: VDRL/RPR (non-specific), confirm diagnosis with specific test (e.g., FTA-ABS).
- Latent syphilis ((+) serology without symptoms) follows.
- Disseminated disease with constitutional symptoms, maculopapular rash (palms and soles), condylomata lata (also confirmable with dark-field microscopy).
- 3° syphilis
- Gummas (chronic granulomas), aortitis (vasa vasorum destruction), neurosyphilis (tabes dorsalis, “general paresis”), Argyll Robertson pupil.
- Signs: broad-based ataxia, (+) Romberg, Charcot joint, stroke without hypertension.
- For neurosyphilis: test spinal fluid with VDRL or RPR.
- Congenital syphilis
- Saber shins, saddle nose, CN VIII deafness, Hutchinson teeth, mulberry molars.
- To prevent, treat mother early in pregnancy, as placental transmission typically occurs after first trimester.
44
Q
Gardnerella vaginalis
- Properties
- Associations
- Characterized by…
- Treatment
A
- Properties
- A pleomorphic, gram-variable rod that is involved in vaginosis.
- Presents as a gray vaginal discharge with a fishy smell
- Nonpainful (vs. vaginitis).
- Associations
- Associated with sexual activity, but not sexually transmitted.
- Characterized by…
- Bacterial vaginosis is also characterized by overgrowth of certain anaerobic bacteria in vagina.
- Clue cells, or vaginal epithelial cells covered with Gardnerella bacteria, are visible under the microscope (arrow) [A].
- Treatment
- Metronidazole or (to treat anaerobic bacteria) clindamycin.
- I don’t have a clue why I smell fish in the vagina garden!
46
Q
Rickettsial diseases and vector-borne illness:
Rash common
- Rocky Mountain spotted fever
- Properties
- Transmission
- Found…
- Findings
- Typhus
- Transmission
- Findings
A
- Rocky Mountain spotted fever
- Properties
- Rickettsiae are obligate intracellular organisms that need CoA and NAD+ because they cannot synthesize ATP.
- Transmission
- Rickettsia rickettsii, vector is tick.
- Found…
- Despite its name, disease occurs primarily in the South Atlantic states, especially North Carolina.
- Findings
- Rash typically starts at wrists and ankles and then spreads to trunk, palms, and soles [A].
- Classic triad—headache, fever, rash (vasculitis).
-
Palms and soles rash is seen in Coxsackievirus A infection (hand, foot, and mouth disease), Rocky Mountain spotted fever, and 2° Syphilis
- You drive CARS using your palms and soles
- Properties
- Typhus
- Transmission
- Endemic (fleas)—R. typhi.
- Epidemic (human body louse)—R. prowazekii.
- Findings
- Rash starts centrally and spreads out, sparing palms and soles.
- Transmission
- Rickettsii on the wRists, Typhus on the Trunk.
47
Q
Rickettsial diseases and vector-borne illness:
Rash rare
- Ehrlichiosis
- Anaplasmosis
- Q fever
A
- Ehrlichiosis
- Ehrlichia; vector is tick.
- Monocytes with morulae [B] (berry-like inclusions) in cytoplasm.
- Anaplasmosis
- Anaplasma, vector is tick.
- Granulocytes with morulae in cytoplasm.
- Q fever
- Coxiella burnetii; no arthropod vector.
- Tick feces and cattle placenta release spores that are inhaled as aerosols.
- Presents as pneumonia.
- Q fever is Queer because it has no rash or vector and its causative organism can survive outside in its endospore form.
- Not in the Rickettsia genus, but closely related.
48
Q
Chlamydiae
- Properties
- Forms
- Chlamydia trachomatis
- C. pneumoniae and C. psittaci
- Treatment
- Lab diagnosis
A
- Properties
- Chlamydiae cannot make their own ATP.
- They are obligate intracellular organisms that cause mucosal infections.
- Chlamys = cloak (intracellular)
- The chlamydial cell wall is unusual in that it lacks muramic acid.
- 2 forms
-
Elementary body (small, dense)
- “Enfectious” and Enters cell via Endocytosis
- Transforms into reticulate body.
-
Reticulate body
- Replicates in cell by fission
- Reorganizes into elementary bodies.
-
Elementary body (small, dense)
- Chlamydia trachomatis
- Causes reactive arthritis (Reiter syndrome), follicular conjunctivitis [A], nongonococcal urethritis, and PID.
- C. pneumoniae and C. psittaci
- Cause atypical pneumonia
- Transmitted by aerosol.
- Chlamydophila psittaci—notable for an avian reservoir.
- Treatment
- Azithromycin (favored because one-time treatment) or doxycycline.
- Lab diagnosis
- Cytoplasmic inclusions seen on Giemsa or fluorescent antibody–stained smear.
50
Q
Mycoplasma pneumoniae
- Properties
- Causes…
- Treatment
A
- Properties
- No cell wall.
- Not seen on Gram stain.
- Bacterial membrane contains sterols for stability.
- Grown on Eaton agar.
- High titer of cold agglutinins (IgM), which can agglutinate or lyse RBCs.
- Causes…
- Classic cause of atypical “walking” pneumonia (insidious onset, headache, nonproductive cough, patchy or diffuse interstitial infiltrate).
- Mycoplasmal pneumonia is more common in patients <30 years old.
- Frequent outbreaks in military recruits and prisons.
- X-ray looks worse than patient.
- Treatment
- Macrolide, doxycycline, or fluoroquinolone (penicillin ineffective since Mycoplasma have no cell wall).
