Micro Midterm 2 Flashcards
How is a diagnosis for M. pneumoniae made?
Usually clinically
Can penicillins and cephalosporins be used to treat M. pneumoniae?
No, because it has no cell wall
Which antibiotics are used to treat M. pneumoniae?
Macrolides and tetracyclines
In an older patient, is Chlamydophila pneumonia more likely to produce a lower or an upper respiratory tract infection?
Lower
How many adults in the U.S. get Chlamydophila pneumoniae per year?
~100k
How is C. pneumoniae transmitted?
Respiratory droplets
Does C. pneumoniae have a cell wall? Does it replicate extracellularly or intracellularly?
Intracellularly
What is an “elementary body” of C. pneumoniae?
It is a metabolically inactive, infectious form that can survive outside a host cell
What is the intracellular form of C. pneumoniae called?
Reticulate body
What genus of bacteria does this diagram illustrate? It is the second-smallest family of prokaryotes known, after Mycoplasma.
Chlamydia
Label the following life cycle states for C. pneumoniae.
Top: elementary body, bottom: reticulate bodies
Why does C. pneumoniae evade host defenses so well?
Replicating intracellularly, it can evade host detection
Is there a higher risk of C. pneumoniae in immunocompromised patients as compared to immunocompetent patients?
It is unclear
What is the annoying symptom of C. pneumoniae that persists for weeks?
A cough that does not subside
Does C. pneumoniae typically cause a fever?
No
Which age group is most likely to get an asymptomatic C. pneumoniae infection?
Children
Symptomatic vs. asymptomatic C. pneumoniae might be associated with the host’s inflammatory predisposition, which could be implied by what vascular condition?
Atherosclerosis
Do most cases of C. pneumoniae result in a diagnosis?
No
Which antibodies can be detected after C. pneumoniae infection that can diagnose its presence?
IgM and IgG antibodies
What is the third-most common cause of atypical pneumonia?
Legionella pneumophila
Is Legionella spread from person to person?
No
Where does L. pneumophila prefer to live?
Aqueous habitats, both fresh and saltwater
How does L. pneumophila transfer from a water source to a person’s respiratory tract?
Aerosolization of the water by e.g. a shower head
What is the incubation period of L. pneumophila?
2-10 days
Why is L. pneumophila an underreported disease?
Generalized typical pneumoniae is often treated with azythromycin, which can also be effective against L. pneumophila, so doctors typically do not end up distinguishing between this and typical pneumonia
What is the shape, size, and gram staining of L. pneumophila?
Small, gram-negative bacilli
Is L. pneumophila an anaerobe or an aerobe?
Obligate aerobe
Which serogroup of L. pneumophila causes 75%-90% of human infections?
Group 1
Does Legionella pneumophila grow on typical bacterial culturing media?
No, it requires special media
What organism is this, which is growing well on buffered charcoal agar? Is this a medium that a lab would typically include in a culture assay?
Legionella; no, this is atypical media
What phagocytoses L. pneumophila when they reach the lungs?
Alveolar macrophages
Can L. pneumophila be deadly? Is there a neutrophil response, or a humoral response, or both? What dying cells trigger a severe inflammatory response?
Yes; both responses occur; dying macrophages
Of the top three atypical pneumonias, which is the most dangerous?
Legionella pneumophila
How can L. pneumophila be diagnosed by lab tests?
Culture of respiratory secretions on selective media, and detection of antigen of serogroup 1 (e.g. via direct fluorescence with antibodies)
What are the mainstays of treatment for L. pneumophila?
Macrolides (azythromycin), tetracyclines, and quinolones
Does L. pneumophila replicate intracellularly or extracellularly? How does this affect choice of treatment?
Intracellularly; antibiotics that reach an effective intracellular concentration must be used
Do clarithromycin and azythromycin require the bacterium to have a cell wall?
No, they block protein synthesis (they are both macrolides)
What are the three most frequent toxic effects of macrolides?
Diarrhea, nausea, abdominal pain
What is the common suffix for fluroquinolone antibiotics? Do they inhibit DNA, RNA, protein, or cell wall synthesis?
-floxacin; inhibit DNA synthesis (topoisomerase and gyrase inhibition)
Can treatment for atypical pneumonia be administered orally?
Yes
How might liver function or kidney function affect choice of a fluoroquinolone?
Levofloxacin and ciprofloxacin are eliminated by the kidneys, while moxifloxacin is eliminated by the liver in bile
What is the most common clinical symptom for a GI infection?
Diarrhea
Do most infections of the GI tract causing diarrhea require hospitalization?
No
What are the big four bacterial pathogens for foodborne diarrheal disease?
Vibrio, campylobacter, shigella, salmonella
What strain of E. coli is particularly significant for diarrheal disease?
E. coli O157
What is the only gram-positive bacterium that causes common diarrheal disease?
Listeria
What are the top two identified bacterial pathogens causing GI disease hospitalization in New York?
Campylobacter and Salmonella
What are the three mechanisms for enteric infection?
Inflammatory (invasion w/ cytotoxin), noninflammatory (adherence w/ cytotoxin), and penetrating
Which bacterial pathogen has the smallest infectious dose? What about the second smallest?
Shigella (100); Campylobacter (1000)
What is the order of magnitude difference between an infectious dose of Salmonella as opposed to Campylobacter?
103 greater for Salmonella (106 cells typical infectious dose)
What is a typical infectious dose for E. coli or Vibrio cholerae?
108 cells
What dangerous symptom does cholera cause via an exotoxin?
Dehydration by diarrhea and vomiting of clear fluid
What bacterium causes cholera and has “cholera” in the species name?
Vibrio cholerae
When was the last epidemic of cholera in the US?
1911
What is the shape of V. cholerae? What is its gram staining? Does it have spores?
Curved to straight bacilli; gram negative; no spores
Which serotypes of V. cholerae cause cholera?
O1 and O139
What is the natural environmental habitat of cholera?
Aquatic environments
What are the non-life-threatening clinical symptoms of cholera, besides diarrhea and vomiting?
Muscle cramps, loss of skin turgor
How does death occur for a cholera patient?
Hypovolemic shock, metabolic acidosis, and uremia from tubular necrosis
What is the chemical activity of cholera toxin? What receptor does it act upon? What intracellular signaller is upregulated, causing loss of cell nutrients?
It is an A-B type ADP-ribosylating toxin; Ganglioside receptor; cAMP
Are antibiotics needed to treat V. cholerae?
No, just rehydration
What is this bacterium that causes bloody diarrhea?
Shigella
Is Shigella lactose-fermenting?
No
Besides bloody diarrhea, what are two other clinical hallmarks of bacillary dystentery?
Abdominal cramps and pain, and tenesmus (painful straining to pass stool)
What does tenesmus mean?
Painful straining to pass stool
What is the reservoir of infectious Shigella?
Humans, it is transmitted person-to-person
What is the pathogenetic mechanism of Shigella infection?
It invades enterocytes and causes cell death
What mechanism of bacillary enteric disease is seen here?
Inflammatory + invasive, as in Shigella infection
What does subunit A of the Shiga toxin do? What about subunit B?
It permanently inactivates ribosomes; it binds to host receptors
Do organisms beside Shigella produce shiga-like toxins?
Yes, some strains of E. coli
Is bacteremia a common complication of Shigella?
No
What are the two species of Salmonella that cause enteric disease?
Salmonella enterica and Salmonella bongori
What is the shape and gram staining of Salmonella? Are they aerobic? Are they motile? Do they form spores?
Gram-negative rods; anaerobic; motile; non-spore-forming
Do Salmonella species produce hydrogen sulfide during fermentation?
Yes
Can Salmonella cause bacteremia? What complication typified by rose spots and delirium can result from salmonella infection?
Yes; typhoid fever
Are there asymptomatic carriers of Salmonella?
Yes, including some that had to be forcibly quarantined
How long does it take for symptoms of Salmonella to present after infection?
48h
What is the shape of Salmonella incidence in the US from year to year?
Spikey because of sporadic outbreaks
What are three common sources of Salmonella infection besides person-to-person contact?
Agricultural products, processed food, and domestic animals
What two cell types are invaded by Salmonella during initial stages of infection?
M cells and intestinal macrophages
How does Salmonella interact with microvilli on certain enterocytes to facilitate endocytosis? Can it invade non-phagocytic cells?
It attracts them, surrounding itself with the cell’s membrane; yes, it can invade many kinds of enterocytes
What areas of the Salmonella genome contribute most to its virulence?
Two pathogenicity islands called SPI1 and SPI2
How does Salmonella survive inside the cell after phagocytosis?
It secretes toxins that prevent fusion of lysosomes with the endosome and then replicates in the endosome
How does Salmonella release its anti-lysosomal fusion toxins into the cytoplasm despite being trapped in an endosome after endocytosis?
Toxins secreted by salmonella (encoded on the pathogenicity island SPI-2) move to the endosomal membrane and allow transport into the cytoplasm of SPI-2 effector molecules
What is this spirally bacterium that causes enteric symptoms, mainly through the handling of chicken?
Campylobacter
What is the shape and gram staining of Campylobacter?
Helical, gram-negative
What is Guillain-Barré syndrome? What is the most common antecedent infection?
An autoimmune disorder that causes peripheral paralysis after foreign antigens cause mistargeting of the immune response toward nerve tissues; Campylobacter
What pathogen is this, causing gastric and duodenal ulcers?
H. pylori
The stomach can normally handle acidity with its mucosal lining, but what happens during H. pylori infection that causes ulceration?
The bacterium invades intercellularly, using secreting toxins to disrupt cell-to-cell junctions
Are most infections for H. pylori symptomatic?
No
What is the most common cause for gastritis, gastric ulcer, and duodenal ulcer?
H. pylori infection
What upper gastric infection that commonly causes gastritis or ulceration is linked to gastric adenocarcinoma?
H. pylori
Can non-selective stool cultures diagnose H. pylori?
No, it is an upper GI infection and it is hard to isolate on non-selective media
What needs to be added to culture to get proper growth of H. pylori from a stool sample?
Bile salts
What tests can distinguish between Salmonella and other enterobacteriaceae?
Citrate and ornithine decarboxylase
What three antibiotic resistances are common with the top four bacterial causes of GI infection?
Amoxicillin (or penicillins), 1st generation cephalosporins, and trimethoprim-sulfamethoxazole
Since GI bacterial infections are resistant to many antibiotics, which ones are actually used for treatment?
Fluroquinolones (-floxacins), 3rd generation cephalosporins (ceftriaxone), and macrolides (azithromycin)
Does daptomycin have gram-negative activity? Why or why not?
No; it cannot penetrate the outer membrane sufficiently to cause depolarization
What are the most common manifestations of Klebsiella infection?
Pneumonia, UTI, and nosocomial infections
How can E. coli be distinguished from K. pneumoniae in the lab, e.g. after a urine sample for a UTI manifestion?
E. coli is indole positive, K. pneumoniae is negative
What is the main reservoir of K. pneumoniae?
The lower GI tract of humans, and secondarily the skin and female genital tract
What media is used here to demonstrate K. pneumoniae and E. coli by the fermentation of lactose?
MacConkey agar, which gives pink colonies
Is K. pneumoniae motile or non-motile? Is it encapsulated?
Non-motile; encapsulated
What common cause of UTIs and pneumonia is seen in this slide?
K. pneumoniae
What test is being performed here to judge the virulence of a K. pneumoniae strain?
The string test, which sees if the isolate is hypermucoviscous (and therefore more resistant to complement-mediated killing)
What kind of intra-abdominal infections are caused by K. pneumoniae?
Liver abscesses, peritonitis, and cholangitis
What is the variant of pneumonia caused by K. pneumoniae called? What is the characteristic type of sputum produced?
Friedländer’s disease; “currant jelly”
Is K. pneumoniae a common infection for immunocompetent hosts?
No
What is the mortality of a K. pneumoniae infection?
Up to 50%
Why does the sputum produced in a K. pneumoniae infection look like currant jelly?
The infection is hemorrhagic and necrotizing
What feature of this CXR is consistent with the typical qualities of K. pneumoniae infection?
Propensity for upper lobes
After E. coli or Streptococcus, what is the next most common bacterium causing acute inflammation of the peritoneum (peritonitis)?
K. pneumoniae
After E. coli, what is the next most common organism isolated in UTIs?
K. pneumoniae
Features that distinguish complicated UTIs from uncomplicated UTIs include renal […], emphysematous pyelonephritis, and catheter-associated UTIs.
Features that distinguish complicated UTIs from uncomplicated UTIs include renal abscesses, emphysematous pyelonephritis, and catheter-associated UTIs.
Features that distinguish complicated UTIs from uncomplicated UTIs include renal abscesses, emphysematous […], and catheter-associated UTIs.
Features that distinguish complicated UTIs from uncomplicated UTIs include renal abscesses, emphysematous pyelonephritis, and catheter-associated UTIs.
Features that distinguish complicated UTIs from uncomplicated UTIs include renal abscesses, emphysematous pyelonephritis, and […]-associated UTIs.
Features that distinguish complicated UTIs from uncomplicated UTIs include renal abscesses, emphysematous pyelonephritis, and catheter-associated UTIs.
Can K. pneumoniae cause skin and skin structure infections?
Yes
What antibiotic are K. pneumoniae almost universally resistant to due to a chromosomal gene encoding an enzyme breaking down the antibiotic?
Ampicillin (and other penicillins)
Which penicillins are effective against Pseudomonas and Klebsiella? What are they often combined with?
Anti-pseudomonal penicillins which include piperacillin, ticarcillin, and carbenicillin; a β-lactamase inhibitor
Which generation(s) of cephalosporins would be used against K. pneumoniae?
3rd or 4th generations, usually cefepime (4th generation)
Does cefepime have activity against gram negatives, gram positives, or both?
Both
How many β lactamases are there?
Thousands
Are ESBL and KPC chromsomal inducible or plasmid-mediated β-lactamases?
Plasmid-mediated
Which β-lactams are reserved for the most sick patients, particularly those with infections from ESBL-containing bacteria?
Carbapenems
What kind of drug is imipenem-cilastatin?
A carbapenem (β-lactam antibiotic)
Which class of β-lactams is shown here?
Carbapenems
What is distinctive about this β-lactam structure? What class is it?
It lacks a ring; it is a monobactam
What is the one monobactam clinically available in the US? Is it active against gram negatives, gram positives, or both? Is it effective against aerobic or anaerobic organisms?
Azteronam; Gram negatives only; Aerobes only
Can monobactams be hydrolyzed by ESBL?
Yes
What is ESBL? When was it first spotted?
It is “extended spectrum β-lactamase”, which confers resistance against all β-lactams except carbapenems; in the 1980’s
If a K. pneumoniae strain is resistant to ceftriaxone but susceptible to imipenem, what kind of β-lactamase does it most likely have?
ESBL
When were variants of K. pneumoniae resistant to carbapenems first discovered? What plasmid-mediated β-lactamase do they typically have?
1990’s; KPC (K. pneumoniae carbapenemase)
Are there other known methods of K. pneumoniae resistance to carbapenems besides KPC?
Yes
What fraction of hospital-detected K. pneumoniae in New York State is carbapenem-resistant?
21%, significantly higher than the rest of the US
Which three other countries are considered endemic or epidemic for carbapenem-resistant K. pneumoniae?
Israel, China, and Greece
What treatment options remain for somebody with carbapenem-resistant K. pneumoniae?
Polymyxin, tygacil, and gentamicin
What is the mechanism of polymyxins? Are they effective against gram-negatives, gram-positives, or both?
They are cationic agents that bind to the outer membrane disrupting its integrity; only gram-negatives
What tissues cannot be penetrated by polymyxins?
Lungs and CSF (cannot cross BBB)
What two toxicities are significant with polymyxins?
Nephrotoxicity and neurotoxicity
What is the mechanism of tigecycline? What class of bacteria is it indicated for treating?
It is similar to tetracyclines, as it inhibits protein synthesis, but resistance to tigecycline is less common than for tetracyclines; effective against gram-negative bacilli like K. pneumoniae
What drug class can be attempted to treat a gram-negative infection in a patient with a severe β-lactam allergy?
Monobactams e.g. aztreonam
What structural component of K. pneumoniae is the most important virulence factor?
Polysaccharide capsule
Is imipenem a cure-all for multidrug-resistant gram-negative infections?
No, carbapenem resistance is on the rise (especially in New York State)
Which species of anaerobic gram positive bacilli is most commonly seen in the hospital?
Clostridium difficile
What organism is most often linked with antibiotic-associated diarrhea?
Clostridium difficile
Which Clostridium causes spastic paralysis? Which causes flaccid paralysis?
- C. tetani*: spastic;
- C. botulinum*: flaccid
Are there many anaerobic bacteria that are normal human commensals?
Yes
When mixed with aerobic organisms, what do anaerobes tend to form?
Abscesses
Do anaerobes produce gas when they metabolize food?
Yes
What is crepitus?
When you push on necrotic tissue and you feel bubbles created by an infectious disease
What antibiotic can be used against most anaerobic infections?
Penicillin, or penicillin with a β-lactamase inhibitor
Besides penicillins, what four other antibiotics are used to treat anaerobic bacterial infections?
2nd generation cephalosporins, carbapenems, metronidazole, and clindamycin
What is the suffix for carbapenem drugs?
NAME?
What is the mechanism of action of metronidazole?
DNA damage
What dietary modifications are necessary when taking metronidazole?
No alcohol
What is the mechanism of clindamycin?
It inhibits the translocation step of bacterial peptide synthesis
A 63 yo woman receives prophylactic cefazolin before surgery for a hip fracture, and develops fever, abdominal pain, and severe diarrhea. Her WBC is elevated and a colonoscopy is performed. What bacterium is most suspect?
Clostridium difficile
Does C. difficile form spores? What is its shape and gram staining?
Yes, it forms spores; it is a gram-positive bacillus
What are three lab tests can be used to make a diagnosis of C. difficile?
EIA toxin assay, cytotoxicity assay, and PCR
What two toxins of Clostridium difficile are detected by PCR?
Toxin A and B, the former is an enterotoxin and the latter is a cytotoxin.
What characterizes a toxic megacolon? What surgical procedure may be required for it?
A massive dilation of the colon and septic shock; it may require a bowel resection
What are the standard treatments for C. difficile?
Metronidazole and oral vancomycin
Why can oral vancomycin treat C. difficile even though it is poorly absorbed by the gut?
C. difficile is a GI infection, and oral vancomycin can act locally on the GI tract without being absorbed
What could allow for C. difficile to survive a course of antibiotics and reappear during a relapse?
Spore formation
What mutation has created hypervirulent strains of C. difficile?
They have lost the repressor region of a toxin gene
What is the average cost of each case of C. difficile-associated disease?
>$3.6k
Will alcohol-based sanitizers remove C. difficile spores from one’s hands?
No
What problem results from using gram stains to distinguish C. perfringes?
It doesn’t always retain the gram stain, so it may not appear positive even though it is gram positive
What kind of hemolysis is distinctive for C. perfringens?
Double zones, one with complete hemolysis, and one with partial hemolysis
What does the India Ink prep reveal about C. perfringens?
The capsule
What toxin causes the zone of complete hemolysis by C. perfringens? What about the partial hemolysis?
Theta toxin: complete hemolysis;
Alpha toxin: partial hemolysis
Can C. perfringens cause soft tissue infections? What about bacteremia?
Yes to both
What is emphysematous cholecystitis? Which Clostridium species can cause it?
Infection of the gall bladder; C. perfringens
The third leading cause of food poisoning, after Campylobacter and Salmonella, is…?
Clostridium perfringens
What is the clinical timecourse for C. perfringens GI infection?
24-48 hours
What are two chief symptoms of C. perfringens infection?
Abdominal cramps and watery diarrhea
What antibiotic is used to treat C. perfringens enteric infection?
Penicillin
What toxin does Clostridium tetani release that causes spastic paralysis and this type of lockjaw? What is this lockjaw called?
Tetanospasmin; risus sardonicus (sardonic smile)
Clostridium**botulinum is associated with what kind of foods?
Improperly canned foods
What kind of neurologic disorder results from the AB toxin released by C. botulinum?
Flaccid paralysis
When a gas is present in a CT scan of infected tissues, what class of organisms can be immediately suspected?
Anaerobic gram-positive bacilli
What forms when commensal flora of the mouth are allowed to enter a normally sterile space? When anaerobic fermentation leads to production of gas, inflating tissues of the neck and compressing the airway, what is this condition called?
Abscesses; Ludwig’s angina
What organism is suggested by a liver abscess growing an anaerobic Gram-negative bacillus?
Bacteroides fragilis
What is the shape and gram staining of Bacteroides fragilis? What enzymes allow it to tolerate oxygen?
Pleomorphic gram negative rod; Catalase and superoxide dismutase
Actinomyces infections can be characterized by what kind of substance that is excreted through the skin?
Sulfur granules, which are actual colonies of the organism
What is the shape and gram staining of of Actinomyces?
Gram positive branching filamentous rod (bacillus)
Where are Actinomyces often found throughout the oral cavity?
In molar tooth cavities
What is the appearance of Nocardia under the gram stain? What stain with a modified pH is used to distinguish it?
Beaded filaments (left); acid fast stain (right)
Is Nocardia a symptomatic infection in immunocompetent hosts?
No
Which bacterium is this, visualized with an acid fast stain?
Nocardia
Which two infectious organisms are both characterized as branching gram positive bacilli? What growth condition can be used to distinguish them? What stain can be used to distinguish them?
Actinomyces and Nocardia; Nocardia can grow aerobically, whereas actinomyces cannot; Nocardia can be stained with acid fast, whereas Actinomyces is not
What is Nocardia treated with?
Trimethoprim-sulfamethoxazole
What gram-positive beaded and fast-growing bacillus is identified with surgical wound infections?
Mycobacterium fortuitum
Does M. fortuitum grow faster or slower than M. tuberculosis?
Faster
What is the gram staining and shape of M. fortuitum?
Gram positive, bacillus
How is M. fortuitum infection of a surgical wound treated?
Debridement, macrolides and β lactams
What gram positive bacillus (preventable with vaccines) can produce an exotoxin that leads to airway constriction and death? What vaccine provides immunity against it?
Corynebacterium diphtheriae; DTaP
The DTaP vaccine protects against tetanus, pertussis, and what other bacterial infection?
Cornyebacterium diphtheriae, causing diphtheria
Is diphtheria common in industrialized nations?
No, not after widespread vaccination programs
How is Corynebacterium diphtheriae treated?
Antitoxin
What organism can cause fatal gas gangrene?
C. perfringes
What does “zoonotic” mean with regard to infections?
Zoonotic means that the pathogen is primarily transmitted to humans from animals
What is the characteristic symptom of diphtheria?
A swollen neck
What organism, causing petechial rashes and altered mental status, is seen in this slide?
N. meningitidis
Is N. meningitidis gram-positive or gram-negative? What is its shape?
Gram-negative; cocci
Why does C. difficile sometimes present in the hospital after prophylactic administration of antibiotics, e.g. cefazolin?
The antibiotics kill the normal gut flora, allowing the C. difficile to replicate without competition
What commonly eaten food is particularly susceptible to Listeria colonization when stored at improper temperatures?
Soft cheeses
What is the primary infective route of L. monocytogenes?
The intestinal epithelium, via an ingested substance
What organism causes spotted fevers (e.g. Rocky Mountain spotted fever) and various types of typhus?
Rickettsia species
What organism causes human monocytic ehrlichiosis (HME)?
Ehrlichia chaffeensis
What organism causes anaplasmosis?
Anaplasma phagocytophilum
What bacterium causes Lyme disease?
Borrelia burgdorferi
What organism is this, which is shown microscopically and with the characteristic rash from infection?
Borrelia burgdorferi
What is the typical shape of a rash for Lyme disease?
Bullseye
In early and late Lyme disease, what heart condition can manifest?
AV block, possibly causing bradycardia
What joint conditions present with long-term Lyme disease?
Swelling and arthritic-like symptoms
What insect is this? What bacterium does this kind of insect spread?
Black legged tick; B. burgdorferi
Where is Lyme disease most common?
Northeastern US and the region around Wisconsin
During what time of year is Lyme disease most likely spread from ticks to humans?
The fall
What animal is the primary host that blacklegged ticks (that carry Lyme disease) feed from?
Deer
Which stage of life of the blacklegged tick is most likely to spread B. burgdorferi to humans?
Nymph, which is after larva and before adult
When are most cases of Lyme disease reported throughout the year?
In a unimodal distribution centered around July
What bacterium is this rash typical of?
B. burgdorferi (Lyme disease)
What is the medical term for the “bullseye rash” caused by B. burgdorferi?
Erythema migrans
During which timecourse after infection are Lyme disease symptoms mostly localized to the site of the tick bite?
3-30 days
1-4 months after a bite containing B. burgdorferi, what general change in the localization of symptoms occurs?
They become more systemic, involving the nervous system, heart, and the rash is disseminated
What two nervous system disorders can result 1-4 months after infection with B. burgdorferi?
Cranial nerve palsy and lymphocytic meningitis
What two signs of cardiac involvement in Lyme disease can occur 1-4 months after the tick bite?
Heart block or myocarditis
What does this patient have? How long has he had it?
Lyme disease (B. burgdorferi); 1-4 months (rash is disseminated)
What are chronic symptoms of late Lyme disease? When do they begin?
Intermittent arthritis and vague neurological symptoms, like radicular pain, paresthesias, and Lyme encephalopathy; 4 months to years after the bite
What is the best way to diagnose Lyme disease? Why?
Clinical picture; antibody and PCR lab tests are not yet reliable, and culturing and staining techniques are not able to demonstrate the organism well
What kind of lab tests are available for Lyme disease? Are they reliable for diagnosis?
IgG and IgM antibody tests and PCR; no, they are not reliable
Why is doxycycline not typically given to children under 8?
It has the potential to stain the teeth (incorporation into anything that is being calcified)
What is the typical course of antibiotics for non-critical manifestations of Lyme disease? What if there is heart block or meningitis?
Amoxicillin for non-critical cases; ceftriaxone for hospitalized cases
What is this bacterium, found in docs and raccoons and potentially transmitted to humans?
Leptospirosis
Which organ systems are affected by leptospirosis?
Liver, kidney, skin, and brain
How does leptospirosis enter the body?
Broken skin or mucosa followed by contact with the organism (e.g. from an infected dog or raccoon)
How is leptospirosis treated? What does the first phase of symptoms present as? What is the source of infection?
Penicillin; flu-like symptoms; animals
Are Rickettsia gram positive or gram negative?
Gram negative
Do Rickettsia species replicate extracellularly or intracellularly?
Intracellularly
What is the reservoir for Rickettsia?
Hard ticks
What disease does R. rickettsii cause that has a 23% case fatality rate?
Rocky Mountain spotted fever
Where is the greatest concentration of the cases of Rocky Mountain spotted fever within the US?
The American Southeast
What are classic clinical manifestations of Rocky Mountain spotted fever?
Fever, headache and rash
What tick-borne disease causes this rash?
Rocky Mountain Spotted Fever (R. rickettsii)
How does Rickettsia induce its own phagocytosis? How does it escape from the phagosome?
By triggering actin rearrangement; release of phospholipase
What food-borne organism is R. rickettsii similar to in terms of how the cells propel themselves and spread to adjacent cells?
L. monocytogenes
Is humoral immunity, cell-based immunity, or both required to clear R. rickettsii? Why?
Cell-based; the organism is mostly confined intracellularly so antibodies cannot bind it directly
What is the shape and gram staining of Ehrlichia and Anaplasma? Do they grow inside or outside of host cells?
Both are tiny round gram negative bacteria; they grow intracellularly
Do Ehrlichia break out of the phagosome after phagocytosis?
No, they tend to stay within the phagosome
Which kind of immune cell is targeted by Ehrlichia chafeensis? Which is targeted by Anaplasma phagocytophillum?
- E. chafeensis*: monocytes;
- A. phagocytophillum*: granulocytes
What kind of insect carries E. chafeensis and A. phagocytophilum?
Ticks
Which other tick-borne disease is carried by the same species of tick that is the reservoir for Lyme disease?
Anaplasma phagocytophilum
Do rickettsia, ehrlichiosis and anaplasmosis patients present reliably with knowledge of a tick bite?
No, they do not recall one in 40% of cases
Of rickettsia, ehrlichiosis, and anaplasmosis, which is least likely to produce a rash? Which is most likely?
Least likely, anaplasmosis; Most likely, rickettsia
What are the symptoms common to rickettsia, ehrlichiosis, and anaplasmosis?
Fever, headaches, myalgia, and malaise
What is the incubation period for rickettsia, ehrlichiosis, and anaplasmosis?
5-10 days
What is the treatment for rickettsia, ehrlichiosis, and anaplasmosis? Should confirmation from the lab be obtained before starting treatment?
Doxycycline; no
What type of lab test can identify rickettsia, ehrlichiosis, and anaplasmosis before the infection runs its course?
PCR (on either infected tissue or blood)
Following a tick bite, should you cover it with petroleum jelly to make it detach itself?
No, you should use tweezers to remove it as soon as possible
What bacterium causes “cat-scratch disease”?
Bartonella henselae
What is the manifestation of cat-scratch disease in a immunocompetent host? What about in an immunocompromised person?
Lymphadenopathy in an immunocompetent person; bacillary angiomatosis (rashes) in immunocompromised
What is the etiology for this kind of rash following a cat scratch? Is it more likely in immunocompetent or immunocompromised patients?
B. henselae infection has caused small tumors in the endothelium of small vessels; immunocompromised patients
What is visualized in a biopsy of a B. henselae related lymphadenopathy?
Granulomas and possibly the organism
What is the shape and gram staining of B. henselae?
Gram negative bacilli
Is B. henselae associated with older or younger cats?
Usually younger cats
What organism causes Q Fever?
Coxiella burnetii
What is the reservoir for C. burnetii?
Cattle, sheep, and goats
How is C. burnetii transmitted from cattle, sheep, or goats to humans? What cell type is infected?
Via inhalation; macrophages
Can you culture C. burnetii?
No, it is a biohazard
How can brucellosis be contracted?
Ingestion of dairy products or contaminated hands, or skin abrasion and contact with infected animals
What common symptom characterizes exposure to C. burnetii and brucellosis? What is the typical source of these pathogens?
Mysterious fevers and myalgia; farm animals like cattle, goats, and sheep
What is the best way to diagnostically confirm most tick-borne diseases? Is it practical to do this before starting treatment?
Serology; no, because serology takes two weeks and some tick-borne diseases are rapidly fatal
What condition are these symptoms immediately indicative of?
Scarlet fever
How is scarlet fever usually treated? What is the most serious side effect?
Penicillin; allergic reaction
A patient that is treated for scarlet fever now presents with this rash. What is most likely to have occurred?
Allergic reaction to penicillin
Which antibiotic has a characteristic adverse effect of bile sludging?
Ceftriaxone
Which antibiotic has the characteristic adverse effect of ototoxicity?
Aminoglycosides
Which antibiotics have the characteristic adverse effect of QTc prolongation?
Azithromycin, fluoroquinolones
Which antibiotic has the characteristic side effect of tendonitis?
Fluoroquinolones
A 2 yo boy presents with 2 days of refusal to walk and fever of 39.5°C. What is the most likely infectious organism? Is this a serious infection? What antibiotic should be used?
S. aureus (most important cause of septic arthritis);
yes;
vancomycin (not nafcillin or ceftriaxone, in case it is MRSA)
Which is the only cephalosporin activate against MRSA?
Ceftaroline, a 5th generation cephalosporin
What outpatient (oral) antibiotics are often active against MRSA?
Clindamycin, doxycycline, and trimethoprim-sulfamethoxazole
What treatment for MRSA can cause myositis or creatinine phosphokinase elevation?
Daptomycin
Which treatment for MRSA has 100% bioavailability? What is its drawback?
Linezolid; besides side effects like bone marrow suppression or serotonin syndrome, it is costly
Which treatment for MRSA can cause Red Man syndrome?
Vancomycin
When a serious S. aureus infection, should a clinician wait until its susceptibility to methicillin is determined before treating?
No, assume it is MRSA and treat accordingly (vancomycin, daptomycin, linezolid, ceftaroline)
An infant presents with fever, lethargy, with no immunizations and a stiff neck. WBC count is elevated and mostly neutrofils, with WBCs present in CSF. What is this infection called? What is the initial treatment until the organism is isolated?
Meningitis; vancomycin and ceftriaxone
From 1 month old throughout adulthood, what are the top three suspects for bacterial meningitis? What is the empirical treatment?
Neisseria meningitidis, S. pneumoniae, and H. influenzae type B; ceftriaxone and vancomycin
What additional cause of meningitis must be suspected in an immunocompromised patient? What antibiotic should be added to the regimen to combat it?
Listeria; ampicillin
Until the age of 1 month, what are the typical suspects for a bacterial meningitis?
Group B streptococcus, E. coli, and Listeria
Which generation of cephalosporins is needed to treat the CNS?
Third generation: ceftriaxone, cefotaxime, ceftazidime
Which β-lactams can be used against pseudomonas?
Cefepime (4th generation cephalosporin), piperacillin-tazobactam (no CNS penetration), carbapenems such as imipenem, azteronam, ceftazidime (3rd generation cephalosporin)
Can Pseudomonas be treated with fluroquinolones?
Yes
What fluoroquinolone is effective against gram negatives and gram positives, including anaerobes?
Moxifloxacin
What is the empiric treatment for a enterococci infection in a patient with neutropenia due to AML? What drug will be used instead if susceptibility is discovered?
Vancomycin, or if resistance is suspected, linezolid and daptomycin; ampicillin
What drugs can be used to treat a C. difficile colitis?
Metronidazole and secondarily oral vancomycin
Are intra-abdominal abscesses going to contain one species, or multiple species? What is the typical pair of antibiotics used?
Multiple; cephalosporin + metronidazole
What is the difference in treatment between typical (community-acquired, lobar) pneumonia and atypical pnemonia?
Typical pneumonia, if treated as an inpatient, uses ceftriaxone and potentially vancomycin if S. aureus is suspected; they are treated similarly as outpatients (azithromycin and levofloxacin)
How many cases of sepsis are diagnosed per year? How many of them result in death?
750,000; 31%
What is the mainstay of treatment for a patient with severe inflammatory response syndrome?
Fluids (normal saline bolus)
Why is oxygen provided to a patient undergoing sepsis?
Oxygen delivery is impaired, e.g., by lack of functional surface area of the alveoli
Out of all the bacterial vaccines that are administered in the US, which has been the least successful in terms of % reduction?
Pertussis (82% reduction)
What federal body sets policy on vaccines?
CDC Advisory Committee on Immunization Practices
Can children under the age of 2 develop memory immunity in response to a polysaccharide antigen?
No
What is the minimum human lethal dose of tetanospasmin? What bacterium produces it?
2.5 ng/kg; Clostridium tetani
What is the difference between an adjuvant and a conjugate vaccine?
A conjugate is the attachment of a protein antigen to create a T dependent response to a normally T independent antigen like a carbohydrate, creating longer-term immune system memory, whereas an adjuvant simply stimulates a nonspecific immune response concurrent with the vaccine antigen exposure
What is the most common route of vaccine administration?
Intramuscular (deltoid or anterolateral thigh)
What two types of immune response are elicited by a mucosal administration of a vaccine?
Systemic and mucosal (IgA) response
What are two methods of mucosal administration of a vaccine?
Oral or intranasal
Are vaccines for the plague and Lyme disease commonly administered today? What about anthrax and tularemia?
No, plague and Lyme disease vaccines are discontinued; anthrax and tularemia vaccines are only given to military personnel
What can be done over time to increase the magnitude and duration of antibody response to a vaccine?
Booster doses
The top four presenting bacterial STD’s are […], chlamydia, gonorrhea, and chancroid.
The top four presenting bacterial STD’s are syphilis, chlamydia, gonorrhea, and chancroid.
The top four presenting bacterial STD’s are syphilis, […], gonorrhea, and chancroid.
The top four presenting bacterial STD’s are syphilis, chlamydia, gonorrhea, and chancroid.
The top four presenting bacterial STD’s are syphilis, chlamydia, […], and chancroid.
The top four presenting bacterial STD’s are syphilis, chlamydia, gonorrhea, and chancroid.
The top four presenting bacterial STD’s are syphilis, chlamydia, gonorrhea, and […].
The top four presenting bacterial STD’s are syphilis, chlamydia, gonorrhea, and chancroid.
Which STDs increase the risk for HIV transmission and why?
STDs that create ulcerative lesions (e.g. syphilis, herpes and chancroid) increase the risk of HIV transmission because of greater exposure between partners of blood-accessible fluids
What bacterium causes syphilis?
Treponema pallidum
High risk groups for syphilis are: men who have sex with men, drug users, and […]
High risk groups for syphilis are: men who have sex with men, drug users, and those with multiple sexual partners.
High risk groups for syphilis are: […], drug users, and those with multiple sexual partners.
High risk groups for syphilis are: men who have sex with men, drug users, and those with multiple sexual partners.
High risk groups for syphilis are: men who have sex with men, […], and those with multiple sexual partners.
High risk groups for syphilis are: men who have sex with men, drug users, and those with multiple sexual partners.
What coats the spirochetes of T. pallidum and protects against phagocytosis?
Host cell fibronectin
Is syphilis a localized or systemic disease? Are most of the symptoms related to toxins released by T. pallidum or the immune response?
Secondary syphilis is systemic, because the spirochete disseminates into the bloodstream; the immune response creates most symptoms
What is the prototypical lesion of syphilis? What does it look like?
The chancre; painless, smooth ulcer with firm borders and clean base.
Why might a patient with syphilis not recognize that they have the chancre (lesion) signalling infection?
It is painless, heals on its own in 3-6 weeks, and may be in an internal or hard to see (perianal, intravaginal) area.
What STD is this lesion prototypical of? What organism causes it? How long does it take for this lesion to heal on its own?
Syphilis; T. pallidum; 3-6 weeks
What kind of a lesion is this? What organism is suspect?
Chancre; T. pallidum (causing syphilis)
What is the shape of T. pallidum?
Spirochete
What are differential diagnoses (related diagnoses that must be ruled out) for a primary chancre that looks like syphilis (T. pallidum)?
Chancroid (H. ducreyi), lymphogranuloma venereum, herpes, and trauma
During secondary syphilis, what clinical manifestations can occur?
Many possible symptoms: rash, fever, malaise, weight loss, diffuse painless lymphadenopathy, pharyngitis, arthralgia, uveitis…
Which STD infection has a secondary stage that this rash a classical sign for?
Syphilis: palm and sole rash
Does the rash of secondary syphilis only occur on the palms and soles?
No, it can also appear on the trunk and elsewhere on the skin
If a patient is asymptomatic for syphilis but as immunoreactivitity to anti-treponemal antibodies, should an LP be taken check for CNS involvement?
This is controversial, so usually it is not done unless the immunoreactivity is very high
What are common symptoms of late syphilis?
Aortitis, CNS complications, and gumma formation
Can T. pallidum be grown on culture? How is it typically visualized?
No; it can be visualized on darkfield microscopy from scrapings of chancres, mucus, or condylomata lata
Is there a treponemal antibody test?
Yes
What is the primary treatment for syphilis? Is there any substitute for this drug in the late stages of the disease?
Penicillin; no
Syndromes of Chlamydia trachomatis that present clinically are: […] infection, infant pneumonia, conjunctivititis, and ocular trachoma.
Syndromes of Chlamydia trachomatis that present clinically are: genital infection, infant pneumonia, conjunctivititis, and ocular trachoma.
Syndromes of Chlamydia trachomatis that present clinically are: genital infection, infant […], conjunctivititis, and ocular trachoma.
Syndromes of Chlamydia trachomatis that present clinically are: genital infection, infant pneumonia, conjunctivititis, and ocular trachoma.
Syndromes of Chlamydia trachomatis that present clinically are: genital infection, infant pneumonia, […], and ocular trachoma.
Syndromes of Chlamydia trachomatis that present clinically are: genital infection, infant pneumonia, conjunctivititis, and ocular trachoma.
Syndromes of Chlamydia trachomatis that present clinically are: genital infection, infant pneumonia, conjunctivititis, and ocular […].
Syndromes of Chlamydia trachomatis that present clinically are: genital infection, infant pneumonia, conjunctivititis, and ocular trachoma.
What is the most common bacterial STD in the US?
C. trachomatis
What is the most common cause of urethritis and epididymitis in US men, and the most common cause of urethritis, cervicitis, and acute salpingitis in US women?
C. trachomatis
Does immunity to C. trachomatis confer long term protection against re-infection?
No
How can C. trachomatis be spread? Can it be spread to a birthed infant?
Via abrasion of the skin; yes, via direct inoculation into the eyes and respiratory tract
What are genital syndromes caused by C. trachomatis?
Cervicitis, urethritis, epididymitis, salpingitis, infertility or ectopic pregnancy
Can Chlamydia cause infertility?
There is a strong relationship, and the pathogenesis is likely via chronic bilateral scarring of the fallopian tubes
What is the shape and gram staining of Neisseria gonorrhea?
Bean shaped gram-negative diplococci
Is N. gonorrhea more likely to spread male to female or the other way around?
Male to female but both are possible
Is N. gonorrhea more or less likely to be transmitted per episode of sex than HIV?
More likely
When is infection by N. gonorrhea most common?
Adolescents and young adults
Besides the genitourinary tract, where else can N. gonorrhea infections manifest?
Anorectal canal, pharynx, and around the liver
Does pharyngitis caused by N. gonorrhea usually present with symptoms? If so, what are they?
No, it is usually asymptomatic
What causes pelvic inflammatory disease?
Usually, a bacterial super-infection secondary to N. gonorrhea infection
What is Fitz Hugh Curtis syndrome?
Perihepatitis caused by N. gonorrhea by direct extension of the organism from the fallopian tubes to the liver capsule
What kind of agar is used to culture N. gonorrhea?
Chocolate agar with antibiotics (Thayer Martin agar)
What is the typical first-line treatment for N. gonorrhea?
Ceftriaxone, 125mg intramuscular once
What is the second line agent of treatment for N. gonorrhea?
Azithromycin
What organism causes Chancroid? Is it more common in the developing world or the US?
H. ducreyi; in the developing world
