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UWorld mixed > #2 microbiology > Flashcards

#2 microbiology Flashcards

1
Q

Haemophilus will not grow on sheep agar unless Staph aureus is plated, why?

A

S. aureus, beta-hemolytic, will lyse RBCs and free hematin (X) and secrete NAD+ (V), which is necessary for H. flu growth

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2
Q

3 types of botulinism

A
  1. foodborne - eating foods w/ botulism toxin (i.e. canned)
  2. wound botulism - toxin production in a wound infected w/ c. botulinum
  3. infant botulism - consumes c. botulinum spores, mature into vegetative toxin producing cells in intestine (i.e. contaminated honey)

all three forms can be fatal – medical emergency

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3
Q

3 most common clinical manfifestation of botulinism, and Rx?

A

3 D’s – dipolpia, dysphagia, dysphonia. 12-46 hrs later. antitoxin to sequester circulating toxin, but can’t stop toxin already in cells. supportive.

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4
Q

most common bacterial causes of acute otitis media, sinusitis, AND bacteria conjunctivitis are… name 3

A
  1. strep pnemoniae
  2. nontypable haemophilus influenza
  3. moraxella cattarrhalis
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5
Q

what fraction of the body’s total immunoglobulis are produced by splenic B cells

A

nearly 50%

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6
Q

acute rheumatic fever and acute post streptococcal glomerulonephritis are both post-strep infections, following what TYPE of infxn?

A
  1. APSGN: either strep skin infxn (impetigo) or strep pharyngeal infxn
  2. rheumatic fever: only with GAS throat infxn
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7
Q

classic triad of arthritis, uveitis/conjunctivitis, urethritis

A

reactive arthritis (HLA-B27 related)

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8
Q

strep pnemoniae cannot grow in the presence of…

A

bile or optochin

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9
Q

commonly used clinical disinfectants [4]? which are sporicidal?

what is formaldehyde/glutaraldehyde used for?

A
  1. alcohols (isopropanol, ethanol) - disrupt membrane, denature proteins. NOT sporicidal
  2. chlorhexidine - disrupt membrane, coagulate cytoplasm. NOT sporicidal
  3. hydrogen peroxide - produces free radicals. SPORICIDAL
  4. Iodine - halogenation of proteins & nucleic acids. SPORICIDAL

formaldehyde/glutaraldehyde – alkylating and cross-linking DNA, sterilize hospital equipment that can’t stand autoclave (high pressure steam

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10
Q

which anti-malarial drug treats hypnozites?

A

primaquine (p=prevent relapse). no effect on merozites!

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11
Q

most serious long-term adverse effect of chloroquine

A

retinopathy!! (primaquine doesn’t have this)

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12
Q

chloroquine resistant malaria rx: [2]

A

mefloquine or quinine/doxycycline

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13
Q

48hour cycle malaria

A

p. vivax or ovale (which have hepatic latent stages)

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14
Q

lechithinase (or phospholipase C) toxin released by?

A

Clostridium perfringens - degrades phospholipids. gas gangrene

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15
Q

pertussis toxin

A

exotoxin by bordetella pertussis – stimulates G-proteins to increase cAMP production. increased insulin (hypoglycemia), lymphocyte & neutrophil dysfunction, and increased histamine sensitivity

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16
Q

shiga toxin (shigella) and shiga-like toxin (e. coli)

A

inactivate 60s ribosomal subunit

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17
Q

microbes that can cause necrotizing fasciitis [5]

A
  • step pyogenes
  • staph aureus
  • clostridium perfinges
  • strep agalactiae
  • aeromonas hydrophila (gram neg rod, non-lactose, oxidase +)
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18
Q

coag -, cat-, PYR+, hyaluronidase, m-protein (prevents complement fixation)

A

strep pyogenes

(s aureus is PYR -)posi

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19
Q

positive cAMP test

A

enhancement of s. agalactiae beta-hemolysis when plated perpendicular to s. aureus

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20
Q

medium for isolation of N. gonorrhoeae

A

thayer-martin;

chocolate agar +

  • vancomycin (inhibit gram +,
  • colistin (polymixin) to inhibit gram negative (inclu other neisserias),
  • nystatin to inhibit yeast, and trimethoprim to inhibit proteus
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21
Q

what do nonspecific treponemal test look for (VDRL, RPR)

A

cardiolipin, by product of treponemal infxn

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22
Q

though it is too thin to see on gram stain, treponema is..

A

gram negative

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23
Q

haemophilus ducreyi

A

forms “chancroid”. similar primary lesion to chancre in syphilis, but painful and swollen regional lymph nodes

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24
Q

histoplasma capsulatum

A

mississippi and ohio river valley. bird and bat droppings. chicken coops and caves.

pulmonary – similar to tuberculosis (lung granulomas w/ calcifications). disseminate to lung, spleen, liver.

hides in macrophages

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25
Q

blastomycoses dermatitidis

A

great lakes. mississippi and ohio river valley.

doubly refractive wall, single broad-based bud

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26
Q

coccidioides immitis

A

southwestern states (desert areas). thick-walled spherules w/ endospores. pulmonary flu-like. disseminated skin, bones, meninges

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27
Q

paracoccidiodes basiliensis

A

also dimorphic. mucocutaneous or cutaneous ulcers. progress to lymph nodes and lung. central and south america.

28
Q

two most common causes of hematogenous osteomyelitis

A
  1. staph aureus

2. strep pyogenes

29
Q

organs affected by cryptococcus neoformas. where is it found?

A
  1. first pulmonary, but often asymptomatic
  2. meningitis

pigeon droppings!

test: red on mucicarmine stain, india ink, serologic testing (latex agglutination) capsular antigen. thick polysacc capsule

can form pulmonary nodules.

30
Q

hot tub folliculitis

A

superficial pseudomonas infection of hair follicle

31
Q

common source of pseudomonas infection

A

water! hot tub folliculitis, swimmer’s ear

32
Q

psuedomonas characterestics

A 
gram neg
non lactose fermenting
oxidase + 
motile
produce pigment (pyocyanin, pyoverdin)
33
Q

which viruses acquire membrane from host nucleus

A

CMV and EBV (herepesviridae family)

34
Q

describe where gp160 is from?

A

encoded from env gene, glycosylated. proteolytically cleaved in ER and golgi to make gp120 and gp41. both needed to bind to CD4 receptor

35
Q

s. epidermidis causing opportunistic infections in which two scenarios?

A
  1. endocarditis in pts w/ prosthetic valves

2. septic arthritis in pts w/ prosthetic joints

36
Q

which staff can ferment mannitol?

A

s. aureus

37
Q

neonates born to HBsAg and HBeAg moms have 1. what risk of chronic infxn 2. replicative rate 3. severity of hepatic injury

A
  1. high risk for chronic infxn
  2. high replicative rate
  3. MILD hepatic injury (not inherently cytopathic)
38
Q

Guillan-Barre key finding and associated pathogen

A

loss of deep tendon reflexes, ascending paralysis
associated w/ history of camplyobacter jejuni infxn (diarrhea)

demyelinating syndrome of peripheral nerves. ascending muscle weakness and paralysis.

39
Q

b. anthracis virulence factors: anthrax exotoxin (edema, lethal, protective) & capsule

A
  1. edema factor: increase cAMP, edema
  2. lethal factor: zinc-dependent protease, inhibits MAPK signaling, causes apoptosis, multisystemic physiologic disruption
  3. protective antigen – translocates edema and lethal factor into cytosol

antiphagocytic poly-y-D-glutamic acid capsule

40
Q

b. pertussis: (1) pertussis toxin and (2) adenylate cyclase toxin

A
  • pertussis toxin: disinhibits adenylate cyclase through Gi ADP ribosylation, increasing cAMP, edema & phagocyte dysfxn
  • adenylate cyclase: increased cAMP, edema & phagocytosis

two toxins, same end effect

41
Q

c. difficile (toxin A and toxin B)

A

toxin A: recruits & activates neutrophils, cytokine release –> mucosal inflammation, fluid loss & diarrhea

toxin B: induces actin depolymerization; mucosal cell death, bowel wall necrosis, pseudomembrane formation

42
Q

s. pyogenes (pyrogenic exotoxin and streptolysis O&S)

A

pyrogenic exotoxin: superantigen, induces fever & shock –> scarlet fever and toxic shock

streptolysin O & S: damages erythrocytes, beta-hemolysis

43
Q

treatment of acute C. diptheriae infection

A
  1. diptheria antitoxin
  2. penicillin / erythromycin
  3. DPT vaccine

toxin infects neural and cardiac tissue. acute infxn affects naso and oropharynx

44
Q

most common cause of death post-C. diptheriae infxn

A

cardiomyopathy. (late neuro effects as well)

45
Q

schistosomiasis [3 types]

A

s. haematobium, urinary
s. mansoni, intestinal
s. japonicum, hepatic

contact w/ freshwater snails, penetrate skin, enter vascular / lymphatics

clinical manifestations –> Th2 mediated immune response against eggs: granulomatous inflammation w/ fibrosis

46
Q

s. haematobium [location and symptoms]

A

north africa, sub-saharan africa, middle east

urinary schistosomiasis: terminal hematuria, dysuria, freq urination, hydronephrosis, pyleonephritis, squamous cell carcinoma of bladder

47
Q

s. mansoni [location and symptoms]

A

sub-saharan africa, middle east, south america, caribbean

intestinal schistosomiasis: diarrhea, abdominal pain, ulceration -> iron deficiency anemia

48
Q

s. japonicum

A

asia [china, philippines, japan]

hepatic schistosomiasis: hepatosplenomegaly, periportal fibrosis, portal hypertension

PIPSTEM FIBROSIS: pathognomonic for hepatic schistosomiasis, caused by eggs settled into presinuosoidal radicals of the portal vein & fibrosis –> portal hypertension

49
Q

diphtheria toxin (exotoxin w/ AB subunits)

A

B – binds growth factor receptor on cardiac and neural cells, induces endocytosis
A – ADP-ribosylation of EF-2

50
Q

nonpulmonary sequelae of mycoplasma pneumonia infection

A

hemolysis, due to antigenic similarity between cell membranes. COLD AGGLUTINATION! stimulates cross-reactive antibodies.

51
Q

how does Diphtheria acquire virulence?

A

bacteriopage-mediated infection w/ tox gene

52
Q

how does strep pneumonia acquire virulence?

A

transformation, ability to produce capsules

53
Q

which bacteria can undergo transformation, take up naked DNA from environment

A

s. pneumoniae, h. flu, neisseria

SHiN

54
Q

complications of herpes zoster

A
  1. post-herpetic neuralgia (rx: topiramate)

2. herpes zoster ophthalmicus, when VZV is in trigeminal n. v1

55
Q

polyprotein viral product that must be cleaved, often made by which family?

A

picornaviridae, i.e. echovirus. typically, single stranded, positive sense, linear, nonsegmented RNA

56
Q

gram-positive cocci able to synthesize dextrans from glucose?

A 
strep viridans (s. mutans and sanguis). 
able to produce insoluble extracellular polysaccharides (dextrans) using sucrose as a substrate). help adhere to surfaces
57
Q

what causes anterior uveitis (inflammation of the iris) [4]

A
  • herpes virus
  • syphilis
  • lyme disease
  • inflammatory conditions like GLA-B27 related diseases and sarcoid
58
Q

K. pneumoniae is a leading cause of what things

A
  • UTI (e. coli is most common
  • spontaneous bacterial peritonitis
  • nosocomial pneumonia
59
Q

HIV-1 provirus. describe 3 structural genes and 6 regulatory genes

A

structural genes: [needed for virion assembly]

  1. gag - antigens in virion core, like nucleocapsid proteins p24 and p7
  2. pol - reverse transcriptase, integrase, protease
  3. env - envelope proteins gp160

regulatory genes:

  1. tat - needed for repl; transcriptionally activates other viral genes. contributes to virulence
  2. rev - needed for repl; facilitates transport of unspliced viral transcripts out of nucleus
  3. vif
  4. vpr
  5. nef - enhance viral repl, downreg cd4 & mhcI expression
  6. vpu
60
Q

common organisms for..

  • urethritis
  • cystitis
  • pyelonephritis
A

urethritis:
- n. gonorrhoeae, c. trachomatis

cystitis:
- e.coli, s. saphrophyticus, p. mirabilis, klebsiella, enterococci

pyelonephritis:
-same as cystitis

61
Q

common demographic for enterococcal endocarditis in men? women? (i.e. post what procedure)

A

elderly men who have recently undergone manipulation of areas colonized by this organism, such as GI or GU tract. in women, post-obstetrical procedure

GU is usu sterile, but can be contaminated w/ colonic flora in perineum

62
Q

cold agglutination associated w/ which 2 infxn?

A
  • mycoplasma pneumonia
  • EBV infection

and hematologic malignancy

63
Q

name cellular receptor: CMV

A

cellular integrins

64
Q

name cellular receptor: EBV

A

CR2 (CD21)

65
Q

name cellular receptor: HIV

A

CD4 and CXCR4/CCR5

66
Q

name cellular receptor: rabies

A

nAcR (nicotinic acetylcholine receptor) on peripheral nerve

67
Q

name cellular receptor: rhinovirus

A

ICAM1 (CD54)

UWorld mixed (60 decks)

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