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USMLE Step 1 > Microbiology--Clinical Bacteria > Flashcards

Microbiology--Clinical Bacteria Flashcards

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USMLE® Step 1 flashcards
1
Q

Staphylococci identification: novobiocin sensitivities

A

on “staph” retreat, there was NO StRES: saprophyticus–resistant; epidermidis–sensitive

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2
Q

Strep identification: optochin and bacitracin

A

OVRPS: optochin–viridans is resistant; pneumoniae is sensitive

B-BRAS: bacitration–group B is resistant; group A is sensitive

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3
Q

green ring around colonies on blood agar

A

alpha hemolytic, Strep pneumoniae or viridans

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4
Q

clear area of hemolysis on blood agar

A

B-hemolytic bacteria: staph aureus, strep pyogenes, strep agalactiae, listeria monocytogenes

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5
Q

how does MRSA gain resistance to methicillin and nafcillin

A

altered penicillin binding protein

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6
Q

infects prosthetic devices and IV catheters by biofilm

A

staph epidermidis

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7
Q

second most common cause of uncomplicated UTI in women

A

staph saprophyticus

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8
Q

“rusty sputum” sepsis in sickle cell anemia and splenectomy

A

Strep pneumoniae: MOPS are Most OPtochin Sensitive: most common cause of meningitis, otitis media (in kids), pneumonia, sinusitis; gram + diplococci, IgA protease

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9
Q

strep species that is associated with dental caries and bacterial endocarditis on damaged valves

A

Strep viridans: mutans-cavities; sanguinis–bacterial endocarditis; optochin resistant, bile does not lyse, catalase -

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10
Q

pharyngitis, scarlet fever, rheumatic fever, glomerulonephritis

A

Strep pyogenes (group A strep); M protein, ASO titer

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11
Q

bacitracin resistant, B hemolytic, colonizes vagina–affects babies

A

Strep agalactiae (group B strep); colonies at 35-37 weeks in pregnant women, if positive, give prophylactic penicillin; hippurate test +

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12
Q

gram+, catalase -, gamma/alpha hemolytic, growth in bile and hypertonic salt

A

Enterococcus (group D strep) E faecalis, faecium

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13
Q

bacteria that colonizes the gut, can cause subacute endocarditis in colon cancer patients

A

Strep bovis

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14
Q

gram positive rods with metachromatic blue/red granules

A

Corynebacterium diphtheriae; black colonies on cystine tellurite agar, beta prophage (with diptheria toxin), Elek test for toxin; toxoid vaccine available

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15
Q

Spore forming gram + bacteria found in soil:

A

bacillus anthracis, clostridium perfringens, C tetani

other spore formers: B cereus, C botulinum, Coxiella burnetii

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16
Q

gram positive, spore forming, obligate anaerobic bacteria

A

clostridium spp

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17
Q

bad bottles of food and honey

A

Clostridium botulinum (preformed heat labile botulinum toxin)

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18
Q

boil-like lesion–ulcer with black eschar that is painless and necrotic

A

cutaneous bacillus anthracis (gram positive spore forming rod); only bacteria with polypeptide D glutamate capsule

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19
Q

flu like symptoms that progress rapidly to fever, pulmonary hemorrhage, mediastinitis, and shock

A

pulmonary anthrax

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20
Q

reheated rice/pasta

A

bacillus cereus–spore forming gram+ that causes nausea and vomiting within 5 hrs of ingestion via preformed toxin cereulide; watery nonbloody diarrhea and GI Pain within 8-18 hrs

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21
Q

ingestion of unpasteurized dairy products/deli meats

A

Listeria monocytogenes: facultative intracellular microbe; rocket tails via actin that allow for cell penetration; only G+ organism to produce LPS

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22
Q

oral facial abscesses that drain through sinus tracts, form yellow sulfur granules

A

actinomyces (gram +, anaerobic, not acid fast)

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23
Q

pulmonary infection in immunocompromised, cutaneous infection after trauma in competent

A

Nocardia (gram+, aerobic, weakly acid fast)

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24
Q

How does mycobacterium avoid immune clearance?

A

cord factor in virulent strains inhibits macrophage maturation and induces release of TNF-alpha; sulfatides (surface glycolipids) inhibit phagolysosomal fusion

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25
Q

“glove and stocking” loss of sensation and cannot be grown in vitro. armadillo reservoir in US

A

Mycobacterium leprae: lepromatous form–low cell mediated immunity with a humoral Th2 response; tuberculoid form–high cell mediated immunity with largely Th1-type mediated response

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26
Q

strong and weak lactose fermenting enteric bacteria

A

Lactose is KEE; Test with macConKEE’S agar; klebsiella/e coli/enterobacter are fast fermenters; citrobacter/serratia are weak fermenters

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27
Q

neisseria gonorrhea vs meningitidis?

A

both are gram negative diplococci; both ferment glucose and produce IgA protease; MeninGococci ferment maltose and glucose; Gonococcal ferment glucose only; gonorrhea often intracellular within neutrophils

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28
Q

epiglottitis, meningitis, otitis media, pneumonia in children

A

HiB, culture on chocolate agar requires V (NAD+) and X (hematin); gram- coccobacillary rod; vaccine has type B polysaccharide conjugated to protein

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29
Q

severe pneumonia,fever, GI and CNS symptoms

A

Legionnaires disease; legionella; gram negative rod; detect with urine antigen; use silver stain, grow on charcoal yeast extract with iron and cysteine; labs show HYPOnatremia

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30
Q

associated with wound and burn infections

A

pseudomonas aeruginosa: gram negative rode, non lactose fermenting, oxidase +; pyocyanin (blue/green pigment); grape like odor; endotoxin and exotoxin (inactivates EF2)

31
Q

What are e coli virulence factors?

A

fimbriae: cystitis/pyelonephritis; K capsule: pneumonia, neonatal meningitis; LPS endotoxin: septic shock

32
Q

microbe invades intestinal mucosa causing necrosis and inflammation. dysentery.

A

EIEC

33
Q

produces heat labile and heat stabile enterotoxins. No inflammation or invasion

A

ETEC

34
Q

adheres to apical surface, flattens villu, prevents absorption

A

EPEC–diarrhea in children

35
Q

HUS e coli

A

EHEC–does not ferment sorbitol (distinguishes from other E coli)

36
Q

Salmonella vs Shigella: flagella

A

only Salmonella have flagella

37
Q

Salmonella vs Shigella: dissemination

A

Salmonella: hematogenously; Shigella: cell to cell, no hematogenous

38
Q

Salmonella vs Shigella: reservoirs

A

Salmonella: many; Shigella: only humans and primates

39
Q

Salmonella vs Shigella: hydrogen sulfide

A

only salmonella

40
Q

Salmonella vs Shigella: antibiotics

A

Salmonella: prolong course; Shigella: shorten course

41
Q

Salmonella vs Shigella: immune response

A

Salmonella: invades mucosa, monocytic response; Shigella: invades mucosa, neutrophil response

42
Q

Salmonella vs Shigella: diarrhea bloody/nonbloody

A

Salmonella: sometimes bloody; Shigella: bloody

43
Q

Rose spots on abdomen, fever, headache, diarrhea

A

Salmonella typhi–typhoid fever, can remain in gallbladder and cause carrier state

44
Q

major cause of bloody diarrhea esp in children

A

Campylobacter jejuni; fecal oral transmission through foods; grows at 42 C; common antecedent to GBS and reactive arthritis

45
Q

rice water diarrhea via enterotoxin

A

vibrio cholerae–toxin permanently activates Gs; grows in alkaline media; oral rehydration

46
Q

transmitted from pet feces; contaminated milk or pork–mimics Crohns or appendicitis

A

Yersinia enterocolitica–causes mesenteric adenitis

47
Q

curved gram - rode that is catalase, oxidase, and urease +

A

helicobacter pylori

48
Q

flu like symptoms, jaundice, photophobia with conjunctival erythema w/out exudate

A

Leptospira interrogans–spirochete; prevalent among surfers and in tropics; water contaminated w/ animal urine

49
Q

natural reservoir is the mouse

A

Lyme disease–big spirochete, facial nerve palsy, arthritis, cardiac AV block, erythema migrans

50
Q

congenital syphilis

A

saber shins, saddle nose, CN 8 deafness, hutchinson teeth, mulberry molars; to prevent treat mother early in pregnancy–transmission occurs after 1st trimester

51
Q

false positives of VDRL test

A

VDRL: viruses (mono, hepatitis); drugs; rheumatic fever; lupus and leprosy

52
Q

Ixodes ticks (deer and mice)

A

anaplasmosis: infection in RBS by rickettsia spp; increased HR, hematuria, use Giemsa stain; lyme disease

53
Q

Cat scratch

A

bartonella spp: bacillary angiomatosis. lymphadenopathy

54
Q

Louse

A

borrelia recurrentis: recurrent fever; variable surface antigens; rickettsia proweseki (endemic typhoid)

55
Q

unpasteurized dairy

A

brucella spp: brucellosis; undulant fever

56
Q

puppies, livestock (fecal oral, ingestion of undercooked meat)

A

Campylobacter: bloody diarrh

57
Q

Parrots, birds

A

chlamydophila psittaci: psittacosis-severe pneumonia, typhoid mimic

58
Q

aerosols of cattle/sheep amniotic fever

A

coxiella burnetii: q fever–mild flu like illness–chronically can cause endocarditis/hepatitis

59
Q

lone star ticks

A

ehrlichiosis: obligate intracellular bacteria that infect/kill WBCs; supress TNF-alpha

60
Q

ticks, rabbits, deer fly

A

tularemia

61
Q

animal urine

A

leptospirosis

62
Q

animal bite, cats, dogs

A

pasteurella multocida

63
Q

dermacentor ticks

A

rickettsia rickettsii: RMSF

64
Q

Fleas

A

rickettsia typhi–endemic typhus

65
Q

Fleas (rats/prairie dogs are reservoirs)

A

yersinia pestis–plague

66
Q

rash starting at wrists/ankles and spreadin to trunk/palms/soles

A

RMSF

67
Q

differential for palm and sole rash:

A

CARS: Cocksackievirus A, RMSF, 2 syphilis

68
Q

rash starting centrally and spreads out, sparing palms and wrists

A

Typhus

69
Q

monocytes with morulae (berry like inclusions) in cytoplasm

A

ehrlichiosis–tick vector

70
Q

granulocytes with morulae in cytoplasm

A

anaplasmosis

71
Q

2 forms of chlamydia

A

Elementary body (small/dense) that is Enfections/Enters cell via Endocytosis and transforms into Reticulate body that Replicates by fission and reorganizes into Elementary body

72
Q

what is unusual about chlamydia cell walls?

A

lack muramic acid

73
Q

high titer of cold agglutinins IgM

A

Mycoplasma pneumoniae: IgM can aggregate or lyse RBCs, no cell wall, membrane has sterols for stabilityq

USMLE Step 1 (36 decks)

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