CLINICAL MICRO Flashcards
What is a representative member of non-enterococcal group D strep?
S. bovis (subacute endocarditis is perforated colon cancer)
Compare the rash of tick-borne rickettsia to that of louse-borne rickettsia
Tick = RMSF = palms and soles to trunk (centripetal); Louse = epidemic typus (R. prowazekii) = trunk to palms and soles (centrifugal)
What are the Sx of Mycobacterium kanasii?
pulmonary TB like Sx
What disease has morulae in granulocyte cytoplasm)
Anaplasmosis (monocyte would be Ehrlichia)
When growing bugs on EMB agar, what do lactose fermenters look like? What does E. coli look like?
Lactose fermenters = purple, E. coli = purple with metallic green sheen
Why is there no vaccine for N. gonnorrhoaea?
Antigenic variation of the pili
What is the natural reservoir of Borrelia burgdorferi?
mouse
Which type of streptococcal infection (anatomically) is most likely to caus glomerulonephritis?
Skin infections (impetigo) but pharyngitis can still cause it
Name 4 species of Clostridium and their respective toxins
C. difficile (Toxin A = enterotoxin/diarrhea. Toxin B = cytoskeletal damage and pseudomembranous colitis), C. tetani (tetanospasmin), C. botulinum (botulinum toxin), C. perfringens (alpha toxin = phospholipase C)
What bug can you get from cattle and sheep amniotic fluid?
Coxiella burnettii (Q fever); veteranarians
Which form of Hansen’s disease is characterized by a Th2 response?
Lepromatous; recall that Th2 is humoral. Since the severity of leprosy depends on CMI, the presence of a humoral response implies a poor CMI which is why it is lepromatous rather than tuberculoid
What stabilizes the membrane of Mycoplasma pneumoniae?
sterols (no cell wall)
Between which 2 bugs does an optochin test differentiate?
Viridans strep (R ) and S. pneumoniae (S)
What is the Jarisch-Herxheimer reaction?
A flu-like syndrome after initiation of penicillin G for syphilis; due to a release of pyrogens from the lysed bacteria
What causes neonatal staccato cough?
Pneumonia caused by C. trachomatis D-K serotypes
Which type of E. coli ferments sorbitol?
Everything but EHEC
What is the triad of Hemolytic Uremic Syndrome? Most common serotype of E. coli to cause? What other bug can cause?
anemia, thrombocytopenia, and acute renal failure; O157:H7; Shigella spp.
What is the vector for Rickettsia prowazekii?
louse
What is Elek’s test?
The test for diphtheria toxin
How would you treat lumpy jaw?
Ampicillin is the DOC for Actinomyces israelli
What serotypes of C. trachomatis cause lymphogranuloma venereum?
L1, L2 , and L3
What bug can be diagnosed by gram positive rods with metachromatic (blue and red) granules?
Corynebacterium diphtheriae
Name 6 spore formers (Hint: 3 are from the same genus)
B. anthracis, C. perfringens, C. tetani, C. botulinum, B. cereus, Coxiella burnetii (Q fever)
What is the most invasive type of Haemophilus influenzae?
Type B
How do you treat C. trachomatis?
Azithromycin (or doxy) with Ceftriaxone for likely Gonorrheal co-infection
What are the 3 main genera of spirochetes?
Leptospira, Treponema, and Borrelia
Name 3 diseases that have a palm and sole rash
Rickettsia rickettsii (RMSF), Coxsackie A16 (hand foot and mouth), Secondary syphilis
Which species of Strep is hippurate positive?
S. agalactiae
Chronic pneumonia in CF patients is usually caused by _________ and the most important virulence factor here is __________
P. aeruginosa; Biofilm
What is the U.S. reservoir for leprosy?
Armadillo foot pads
Which fastidious gram negative rod will cause hyponatremia?
Legionella pneumophila
What bug has morulae? Vector?
Eherlichia chaffeensis; Lone star tick
What 2 Chlamydial spp. Cause atypical pneumonia?
C. pneumoniae and C. psitiacci
Why is Staphylococcus aureus so good at forming abscesses?
The presence of coagulase (i.e. they are the ONLY coagulase positive G + organism) allows for formation of a fibrin clot and sequestration from the immune system
What is another name for Weil’s disease?
Icterohemorrhagic leptospirosis
What E. coli virulence factors are most important for cystitis and pyelonephritis?
Fimbrae
What bacteria does someone likely have if the X-ray looks worse than the patient?
Mycoplasma pneumoniae
Which type of E. coli flattens villi?
EPEC (P for Peds)
What are the 3 type of anthrax infection?
GI, cutaneous, and pulmonary
What causes diabetic osteomyelitis and sickle cell osteomyelitis?
DM = P. aeruginosa (prob an extension of skin infection of an ulcer) HbS = Salmonella enteriditis
How would you know if an infectious facial palsy was Ramsay-Hunt or Lyme disease?
Ramsay-Hunt syndrome is a VZV bell’s palsy and is unilateral with blistering; Lyme disease is bilateral
Which form of leprosy will have a high Th1 count?
Tuberculoid leprosy; the spectrum of tuberculoid–>lepromatous all depends on CMI
What is the cause of undulant fever?
Brucella
What are 2 possible outcomes of streptococcal pharyngitis that self resolves?
Rheumatic fever and PSGN
What is the gram stain of a bug causing a cherry red epiglottis?
Gram negative coccobacillus
What is the Cioccio general rule for gram positive sensitivities (i.e. novobiocin, bacitracin and optochin)?
Each antibiotic is used to differentiate between 2 bugs, in all cases the bug causing the more severe disease is SENSITIVE to the antibiotic while the less severe bug is resistant to the antibiotic (if you don’t believe me see FA p. 127)
The bacteria grown on Eaton’s agar is common in what 2 demographics?
M. pneumoniae is common in military recruits and prisons
What serotypes of C. trachomatis cause blindness in Africa? What is the pathogenesis here?
A, B, and C? Flies transmit the bug and it causes conjunctivitis with scarring, this occurs over and over again until blind
What do C. trachomatis serotypes L1, L2 and L3 cause?
Lymphogranuloma venereum
What causes aortic aneurysm in tertiary syphilis?
arotitis with destruction of vasa vasorum
What bacteria are carried by these ticks A) Ixodes B) Lone star C) Dermacentor
A) Babesia and B. burgdorferi B) E. chaffeensis C) R. ricketsii (RMSF)
What would you likely see on CXR of a person with Woolsorter’s disease?
Pulmonary hemorrhage and mediastinal widening (B. anthracis)
What is the Tx for Tuberculoid leprosy? Lepromatous?
Tuberculoid = dapsone and rifampin 6 months; Lepromatous = dapsone, rifampin, and clofazimine 2-5 YEARS
A cherry red epiglottis is likely caused by what organism? What sign on CXR?
Haemophilus influenzae B; Thumbprint sign (Steeple sign = Croup, parainfluenzae)
If you ran an electrolyte panel on a patient with Legionairres’ what would you see?
Hyponatremia
How can you differentiate EHEC from other E. coli?
EHEC does not ferment sorbitol
What immune cell infiltrate will you find in the crypts of Salmonella infections vs. Shigella infections?
Salmonella = monocytic; Shigella = PMN
What is the vector for Ehrlichia chaffeensis? What is the typical inclusion body seen?
Lone star tick; morulae
What are your 2 options for treating Mycoplasma pneumoniae?
Macrolide or fluoroquinolone (NO beta lactams bc no cell wall)
What bug causes mediastinal widening?
Pulmonary anthrax
What 2 antibiotics are frequently implicated in pseudomembranous colitis?
ampicillin (beta lactam) and clindamycin (50 S ribosome peptidyltransferase inhibition)
What are the pros and cons to having Anti-M protein antibodies?
Pros: enhances defenses against S. pyogenes, Cons: causes rheumatic fever and PSGN
Everyone knows that alcoholics and DM are the ones who get Klebsiella pneumoniae? BUT WHY?
It is a normal flora of the intestine thus, it gets aspirated? Alcoholics are notorious for aspirating. I’m guessing the DM is because they have autonomic neuropathy and therfore diabetic gastroparesis leading to increased likelihood of aspiration
What is the largest spirochete? What is the thinnest?
Borrelia; Leptospira (lepto = thin)
What is the presentation of primary syphilis? Secondary syphilis?
Primary = painless chancre; Secondary = copper colored maculopapular rash with condyloma lata
Why doesn?t S. aureus require a damaged valve or a pre-existing thrombotic (noninfectious) endocarditis to form bacterial endocarditis while S. epidermidus does?
Because it contains coagulase and can form a fibrin clot around itself which allows it to stick to the valve? S. epi can bind if the valve is damaged and a thrombus has formed on it.
How do you differentiate the Group D strep?
Enterococci grows in 6.5% NaCl and bile; S. bovis only grows in bile
What are the vectors for the 2 spp of Borrelia?
B. burgdorferi = ixodes tick; B. recurrentis = louse
What bug is transmitted by the lone star tick?
Eherlichia chaffeensis
How do you kill spores as in ones that may be leftover on surgical equipment?
Autoclave at 121 C for 15 min
What 2 exotoxins are produced by Clostridium difficile?
Toxin A = enterotoxin causing diarrhea? Toxin B = cytotoxin that damages cytoskeleton of enterocytes = pseudomembranous colitis
How do you treat Listeria monocytogenes?
Ampicillin? But usually only infants, IC pts, and in empirical Tx of meningitis because Listeria gastroenteritis in adults is self-limiting
What do both M. meningitidis and M. gonorrhoeae ferment?
Glucose but meningitidis also metabolizes maltose
In which portion of the bacterial growth curve is an endospore going to form, why?
Stationary phase (top of curve) because this is when growth = death, this is because nutrients are sparse, when nutrients are sparse they initiate survival mode = spore
How do you Tx gonorrhea?
Ceftriaxone (3rd gen) with Azithromycin for likely Chlamydial co-infection
What do serotypes A, B, and C for C. trachomatis cause?
Blindness in Africa
Which type of E. coli produces similar Sx to Shigella but does NOT produce toxin?
EIEC, the invasion causes bloody diarrhea like Shigella
Where does TB usually go when it reactivates and why?
apices of lung because higher ventilation
2 diseases that may present with a saddle nose
Congenital syphilis and Lepromatous leprosy (destruction of septum)
What are the neurological and cardiac manifestations of Lyme disease?
Neuro = bilateral facial palsy (early) and encephalopathy/polyneuropathy (late); Cardiac = AV node block
What bacteria contains a cell wall lacking muramic acid?
Chlamydia
What is the treatment of the 2 filamentous gram positive rods?
Actinomyces = ampicillin; Nocardia = sulfonamides
FTA-ABS is a confirmatory test for what?
Treponema pallidum
What are 4 signs of congenital syphilis?
Mulberry molars, Saber shins, CN VIII deafness, and Saddle nose
Which bacterium inhibits the release of neurotransmitters from Renshaw cells?
C. tetani? Renshaw cells in the spinal cord release inhibitory NTs (GABA and Glycine). Tetanospasmin inhibits their release = spastic paralysis
Aside from the bacitracin test, what are 2 other tests you can use to identify S. agalactiae?
Hippurate test positive and CAMP positive
What is the Tx of Lyme disease (2 drugs), why can’t they go in the sun?
Doxycycline and Ceftriaxone (Doxycycline = a tetracycline, phototoxicity is a notorious AE for this drug)
What is the vector for Rocky Mountain Spotted Fever?
Dermacentor tick
What chemical is added to elicit a positive whiff test for BV?
KOH
What is the screening test for Syphilis? Confirmatory?
VDRL and RPR; FTA-ABS
Which infectious agent leads to a glove and stockings loss of sensation? What disease more commonly does this?
Hansen’s disease (leprosy); Diabetes mellitus
Which antibiotics require O2 for uptake and are ineffective against anaerobes?
Aminoglycosides
What kind of media can Vibrio cholerae grow in? What is the most important aspect of MGMT?
alkaline; REHYDRATION
What causes a thumbprint sign on CXR? Steeple sign?
Thumbprint sign = Haemophilus influenzae B epiglottitis; Steeple Sign = Croup, parainfluenza virus
What shape of gram negative organisms do you use lactose fermentation as an initial measure for differentiation?
Rods? If you have diplococci then you use maltose, if you have coccobacilli then you are dealing with some weird organisms that are fairly fastidious