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USMLE Step 1 > Microbiology-Bacteria > Flashcards

Microbiology-Bacteria Flashcards

1
Q

bacterial structures that induce TNF and IL1

A

Liptechoic acid (cell wall component unique to gram+); Lipid A (o polysaccharide antigen unique to gram - )

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2
Q

contains D-glutamate in capsule

A

Bacillus anthracis

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3
Q

cell membrane with sterols, no cell wall

A

mycoplasma

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4
Q

cell walls/membrane contain mycolic acid with high lipid content

A

mycobacteria

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5
Q

Bugs that do not gram stain well:

A

Treponema, mycobacteria, mycoplasma, Legionella, Rickettsia, Chlamydia (these microbes may lack real color)

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6
Q

Giemsa stain

A

Chlamydia, borrelia, rickettsiae, trypanosomes, plasmodium (Certain bugs really try my patience)

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7
Q

PAS stain

A

stains glycogen (used to diagnose Tropheryma whipplei)

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8
Q

Ziehl Neelsen stain (carbol fuchsin)

A

Acid fast organisms like nocardia or mycobacterium

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9
Q

India ink

A

cryptococcus neoformans (mucicarmine can stain capsule red)

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10
Q

Silver stain

A

Fungi (pneumocystis), legionella, helicobacter pylori

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11
Q

H influenzae growth requirements:

A

Chocolate agar containing NAD+ and hematin

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12
Q

Neisseria gonorrhea, Neisseria meningitidis growth requirements

A

Thayer Martin (VPN media) vancomycin, polymyxin, nystastin

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13
Q

Bordatella pertussis growth requirements

A

Bordet Gengou potato agar

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14
Q

C diptheriae growth requirements

A

tellurite agar, loffler medium

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15
Q

M tuberculosis growth requirements

A

Lowenstein Jensen agar

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16
Q

M pneumoniae growth requirements

A

Eaton agar, requires cholesterol

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17
Q

Lactose fermenting enterics growth requirements

A

pink colonies on macConkey agar (fermentation produces acid, turning colony pink); E coli is also grown on eosin methylene blue agar as colonies with green metallic sheen

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18
Q

Legionella growth requirements

A

charcoal yeast extract agar buffered with cystein and iron

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19
Q

fungi growth requirements growth requirements

A

sabouraud agar

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20
Q

What are some obligate aerobes?

A

Nocardia, Pseudomonas, MycoBacterium (nagging pests must breath)

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21
Q

What are some obligate anaerobes?

A

Closteridium, Bacteroides, actinomyces (can’t breath air)

22
Q

antibiotic that requires O2 to enter bacterial cell?

A

amino2glycosides; ineffective against anaerobes

23
Q

Obligate intracellular

A

rickettsia, chlamydia (can’t make own ATP)

24
Q

Facultative intracellular

A

Salmonella, Neisseria, Brucella, Mycobacterium, Listeria, Francisella, Legionella, Yersinia pestis

25
Q

bacteria opsonized and cleared by spleen

A

Encapsulated bacteria: streptococcus pneumoniae, Haemophilus influenzae type B, Neisseria meningitidis, E coli, Salmonella, Klebsiella pneumoniae, group B strep (SHiNE, SKiS)

26
Q

Which vaccinations to give asplenics?

A

S pneumo, H influ, N meningitidis vaccinations, which are conjugate vaccines that have polysaccharide capsule antigens conjugated to a carrier protein to enhance immunogenicity

27
Q

NADPH oxidase deficient person is susceptible to..?

A

CGD, recurrent infections with catalase positive organisms: Psuedomonas, Listeria, Aspergillus, Candida, E coli, S aureus, Serratia (PLACESS for your cats)

28
Q

Urease positive bugs

A

Cryptococcus, H pylori, Proteus, Ureaplasma, Nocardia, Klebsiella, S epidermidis, S saprophyticus

29
Q

yellow sulfur granules w/ filaments of bacteria

A

actinomyces israelii (israel has yellow sand)

30
Q

yellow pigment

A

S aureus (Au = gold)

31
Q

blue green pigment

A

Pseudomonas aeruginosa (aerugula is green)

32
Q

red pigment

A

Serratia marascens (maraschino cherries are red)

33
Q

Protein A

A

Binds Fc region of IgG and prevents opsonization and phagocytosis–expressed by S aureus

34
Q

IgA proteus

A

Enzyme that cleaves IgA; secreted by S pneumoniae, HiB, Neisseria (SHiN) to colonize respiratory mucosa

35
Q

M protein

A

prevents phagocytosis–group A streptococci; binds to serum factor H, destroying C3-convertase and preventing opsonization by C3b; plasma B cells can generate antibodies against M protein which will help in opsonization and further the destruction of the microorganism by the macrophages and neutrophilis. Cross-reactivity of anti-M protein antibodies with heart muscle is the basis for rheumatic fever

36
Q

Exotoxin vs Endotoxin heat stability?

A

Exotoxins are destroyed rapidly at 60 C except for Staph enterotoxin. Endotoxins are stable at 100 C for 1 hr.

37
Q

Pharyngitis with pseudomembranes in throat and severe lymphadenopathy (bull neck)

A

Corynebacterium diphtheriae: diptheria toxin–inactivate elongation factor (EF-2)–>inhibit protein synthesis; ADP ribosylating A-B toxin

38
Q

Toxin released by pseudomonas aeruginosa

A

Exotoxin A: inactivates EF2–>inhibit protein synthesis, ADP ribosylating A-B toxin

39
Q

GI mucosal damage resulting in dysentery; also causes HUS

A

Shigella (shiga toxin)–inactivates 60S ribosome by removing adenine from rRNA; cytokine release–>HUS; ADP-ribosylating A-B toxin

40
Q

causes HUS, but does not invade host cells (unlike Shigella)

A

EHEC (O157:H7)–shiga like toxin–inactivates 60S ribosome by removing adenine from rRNA; cytokine release–>HUS; ADP ribosylating A-B toxin

41
Q

watery diarrhea, E coli toxin

A

ETEC: heat labile toxin–overactivates adenylate cyclase–increased chloride secretion in guy and water efflux; heat stable toxin overactivates guanylate cyclase–>decreases resorption of NaCl and H2O in guy

42
Q

toxin likely responsible for characteristic edematous borders of black eschar in cutaneous anthrax

A

bacillus anthacis–edema factor–mimcs adenylate cyclase enzyme–increases cAMP

43
Q

voluminous rice water diarrhea

A

vibrio cholerae–cholera toxin–overactivates adenylate cyclase by permanently activating Gs–>increased Cl secretion in gut and water efflux; ADP ribosylating A-B toxin

44
Q

toxin that released by bacteria associated with whooping cough

A

bordatella pertussis–pertussis toxin–overactivates adenylate cyclase by disabling Gi, impairs phagocytosis to permit microbe survival

45
Q

spasticity, risus sardonicus, “lockjaw”

A

Clostridium tetani–tetanospasmin–protease that cleave SNARE proteins required for neurotransmitter release; prevents release of inhibitory GABA/glycine from Renshaw cells in spinal cord

46
Q

Flaccid paralysis, floppy baby,

A

clostridium botulinum–botulinum toxin–protease that cleave SNARE proteins required for neurotransmitter release; prevents release of stimulatory Ach signals at NMJ–>flaccid paralysis

47
Q

myonecrosis (gas gangrene) and hemolysis (double zone on blood agar)

A

Clostridium perfringens–alpha toxin–phospholipase (lecithinase) that degrades tissue and cell membranes

48
Q

hemolysis, ASO used to diagnose rhematic fever

A

streptococcus pyogenes–streptolysin O–protein that degrades cell membrane–lyses RBCs

49
Q

toxic shock syndrome, scalded skin syndrome

A

staph aureus–toxic shock snydrome toxin (TSST-1); brings MHCII and TCR in proximity to outside of antigen binding site to cause overwhelming release of IFN-gamma and IL2–>shock

50
Q

toxic shock syndrome: fever rash shock

A

streptococcus pyogenes (exotoxin A); same mechanism of action as TSST-1

51
Q

Endotoxin (gram negatives) has what actions?

A

activates macrophages–IL1, TNF, NO; activates complement–C3a, C5a; activates tissue factor–coagulation cascade/DIC

52
Q

which bacterial toxins are encoded in a lysogenic phage

A

ABCDE: ShigA-like toxin, Botulinum toxin, Cholera toxin, Diptheria toxin, Erythrogenic toxin of Strep Pyogenes (Strep O)

USMLE Step 1 (36 decks)

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