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GI > MICRO: Specifics > Flashcards

MICRO: Specifics Flashcards

1
Q

How does shigella invade?

A

proliferate in epithelial cells and move into LP where is is phagocytosed by macrophages and will apoptose them and lead to inflammation and damage. Spreads via F-actin polymerization (formins)

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2
Q

Treatment for shigella.

A

Ceftriaxone, Ciprofloxacin, Azithromycin

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3
Q

1 week incubation, 1 week illness.

A

Shigella

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4
Q

How does shiga toxin work?

A

B: binds toxin to cell
A: enters cytosol and removes adenine from large 28S ribosomal subunit to inhibit protein synthesis and cause death

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5
Q

How long is EHEC infection?

A

8 days

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6
Q

How do you treat EHEC?

A

DON’T! Antibiotics can lead to HUS

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7
Q

How does HUS work?

A

Shiga toxin is absorbed from GI mucosa into circulation where it alters endothelial cell funciton to activate platelets and cause aggregation. Hemolytic anemia occurs (shistocytes occur as RBCs pass through clotted off area) and renal failure (receptors for shiga on kidney epithelium) and thromboyctopenia (platelets aggregate)

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8
Q

How do you treat HUS?

A

dialysis

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9
Q

How does EIEC invade?

A

Invades colon and proliferates in epithelial cells, extending into adjacent intestinal cells

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10
Q

How long does EIEC last?

A

1 week

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11
Q

1-3 day incubation, 3-4 day illness.

A

Salmonella enteritidis

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12
Q

How does salmonella enteritidis infect?

A

type III secretion system, bacteria grows in endosomes and enters LP where it causes inflammatory response and kills macrophages (may disseminate if immunocompromised)

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13
Q

How do you treat salmonella enteritidis?

A

DON’T unless at risk for dissemination (then use flouroquinolones)

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14
Q

5-21 day incubation, 3 week-3 month illness

A

Salmonella enterica (serotype typhimurium)

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15
Q

How does typohoid fever infect?

A

Taken up in small intestine, invades, macrophage take up and go to lymph tissue which dumps into the RES system. Can enter blood (bacteremia), can proliferate in peyer’s patch (necrosis, perforation, secondary bacteremia), or can chronically carry in GI.

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16
Q

How do you diagnose typhoid fever?

A

blood cultures

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17
Q

How do you treat typhoid fever?

A

Ceftriaxone, Ciprofloxacin, Azithromycin

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18
Q

Incubation 1 week, 3-7 day illness

A

Campylobacter jejuni

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19
Q

How does Guillian Barre occur?

A

molecular mimicry where antibody to C. jejuni cross reacts with peripheral and CNS gangliosides (ascending paralysis)

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20
Q

How do you treat campylobacter jejuni?

A

Usually don’t, only treat severe infections: ciprofloxacin or azithromycin

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21
Q

What are the 2 bugs that cause inflammatory diarrhea that are NOT GN anaerobic rods?

A 
Clostridium Difficile (gram positive rods)
Yersinia Enterocolitica (gram neg coccobacilli)
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22
Q

What is the overall effect of C. diff exotoxins?

A

glucosylation of small GTPases (ex. Rho) that are involved with cytoskeletal structure and signal transduction

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23
Q

What type of exotoxin is c. diff toxin A?

A

enterotoxin

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24
Q

What type of exotoxin is c. diff toxin B?

A

cytotoxin

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25
Q

What is the action of c. diff toxin A?

A

disrupts colon epithelial cell Adherence to bassement membrane and damages the villous tips (leading to fluid secretion)

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26
Q

What is the action of c. diff toxin B?

A

depolymerizes actin to decrease cytoskeletal integrity and cause apoptosis of enterocyte

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27
Q

What is the common pathway of c. diff toxins A and B?

A

increase monocytes and macrophages to increase IL-8, recruit PMNs, and disrupt epithelial tight junctions

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28
Q

How do you diagnose c. diff?

A

PCR or EIA for toxins (cell culture cytotoxicity assay, but can be negative)

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29
Q

How do you treat c. diff?

A

Metronodiazole (Flagyl) is first line.
PO Vancomycin for severe infeciton
Fidaxomycin (newer)

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30
Q

How does yersinia enterocolitica cause pain?

A

multiply in lymphoid tissue and causes LN and peyer patch hyperplasia (ileum, appendix, and right colon)

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31
Q

How do you treat yersinosis?

A

most cases do NOT warrant treatment

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32
Q

What is a common feature of (all but 1) of the bugs that causes non-inflammatory diarrhea?

A

gram negative anaerobic rods

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33
Q

What is the only bug that causes non-inflammatory diarrhea that is NOT a gram negative anaerobic rod?

A

Staph aureus

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34
Q

How does ETEC cause infection?

A

Produces 2 toxins that both increase Cl- and H2O secretion into the intestinal lumen

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35
Q

What are the names of the ETEC toxins?

A

LT and ST

36
Q

What is the action of LT?

A

(like cholera)–> stimulates adenyl cyclase to increase cAMP and lead to increase Cl- secretion from crypt cells and decrease absorption of NaCl from villous tips

37
Q

What is the action of ST?

A

activates enterocyte cGMP to stimulate Cl- secreiton and inhibition of NaCl absorption from villous tips

38
Q

How long does an ETEC infection persist?

A

1-5 days

39
Q

How does EPEC cause infection?

A

Type III secretion system with LEE (pedestal formation on host surface) which causes diarrhea.

40
Q

How does vibrio cholera cause infection?

A

Mucinase dissolves glycoprotein in intestine and colonizes to then produce the AB Cholera toxin

41
Q

How does the cholera toxin work?

A

B: binds to enterocyte
A: ADP ribosylates Gs to stimulate adenyl cyclase to increase cAMP and PKA and lead to increase Cl- secretion from crypt cells

42
Q

How do you diagnose vibrio cholera?

A

TCBS or TTGA agar, colorless on McConkey

43
Q

How do you treat vibrio cholera?

A

Aggressive volume repletion
Tetracycline, Cipro, Azithromycin, Erythromycin
Oral vaccine available

44
Q

1 day incubation, 3 day watery diarrhea.

A

vibrio parahemolyticus

45
Q

What do you use to treat vibrio parahemolytius (if severe)?

A

volume repletion

doxycycline

46
Q

How do you treat vibrio bulnificus?

A

doxycycline + cefotaxime/ceftriaxone

47
Q

How does staph aureus cause infection?

A

heat stable enterotoxin that acts as superantigen to increase IL-1 and IL-2 from macrophages and helper T cells

48
Q

1-6 hour incubation, </= 24 hour illness

A

Staph aureus

49
Q

8-16 hour incubation, 6-24 hour illness

A

Bacillus cereus

50
Q

How does B. cereus cause infection?

A

Spores ingested and illness cause by the emetic (cereulide) and diarrheal toxins

51
Q

What enzymes do anaerobes of the GI tract lack?

A 
superoxide dismutase (cannot get rid of O2-)
catalase (can't get rid of H2O2)
52
Q

Anaerobic GN Bacillus, Capsule, Normal Flora

A

Bacteriodes Fragilis

53
Q

How do you treat bacteriodes fragilis?

A

Metronidazole, Carbapenems, Beta-Lactams + Beta-lactamase inhibitors

54
Q

Anaerobic GN coccobacilli, opportunistic, normal flora.

A

Prevotella melaninogenica

55
Q

Anaerobic GP bacilli, spore formers

A

Clostridium species

56
Q

Slender, curved motile with polar flagella; Microaerophilic

A

Helobacter pylori

57
Q

What two stomach infections require a HUGE infectious dose to cause infeciton?

A 
Vibrio cholera (killed by stomach acid)
Clostridium perfringens (low infectivity)
58
Q

What bacteria is resistant to heat but its toxins are NOT?

A

clostridium botulinum

59
Q

8-16 hour incubation with a 24 hour infeciton.

A

Clostridium perfringens

60
Q

How do you treat tetanus?

A

Wound debridement
HTIG (neutralize toxin)
Metronidazole or Penicillin
3 doses of tetanus toxoid

61
Q

How do you treat botulism?

A

mechanical ventilation/support
>1 yo get Horse Anti-toxin
<1 yo get Human-Derived botulism immune globulin (BIG-IV)
Do NOT use antibiotics for GI infection (only if skin)

62
Q

How do you diagnose H. pylori infeciton?

A

Stool antigen
urea breath test
endoscopy with culture

63
Q

What are the virulence factors for H. pylori?

A

VacA
PAI (type III secretion system)
CAG
Urease

64
Q

How do you treat H. pylori?

A

triple or quadruple therapy (PI with 2 or more antibiotics)

65
Q

DS, linear DNA virus

A

Adenovirus (40, 41)

66
Q

SS+ RNA virus (non-segmented)

A

Human Astrovirus 1-8

Norovirus

67
Q

SS+ RNA virus (segmented)

A

enterovirus

68
Q

DS RNA virus (segmented)

A

Rotavirus

69
Q

Which viral infection has the quickest incubation period?

A

norovirus (12 hour to 1 day incubation)

70
Q

Which viral infection has the longest incubation period?

A

enterovirus (7-14 days)

71
Q

Where does adenovirus replication occur?

A

Nucleus

72
Q

How is norovirus different from cholera toxin?

A

the glucose coupled Na+ is impaired by norovirus (which infects villi of small intestine and leads to loss of the lining) but the cAMP is NOT stimulated

73
Q

Where does enterovirus replication occur?

A

RNA virus (+) strand so by host ribosomes in the cytoplasm

74
Q

What is unique about enterovirus replication?

A

translation of the RNA by host ribosome yields a large popypeptide that gets self-cleaved by viral encoded proteases to form the RNA polymerase

75
Q

How do you diagnose enterovirus?

A

throat swab

76
Q

Which virus can undergo drift?

A

Norovirus and Rotavirus

77
Q

Which virus can undergo shift and drift?

A

rotavirus

78
Q

What is cool about the structure of rotavirus?

A

has 2-3 concentric icosahedral capsids

79
Q

What is unique about rota virus replication?

A

capsid proteins processed, delivery to late endosomes or lysosomes, enzymes within core synthesize mRNA (assymetric so only (+) stands that are capped but NOT polyadenylated)

80
Q

How does rotavirus cause infection?

A

infects villous epithelium (like norovirus) but also has NSP4 enterotoxin that leads to calcium dependent Cl- secretion

81
Q

What is Rotateq?

A

Live, attenuated 5 bovine human reassortment virus serotypes (G1-G4 and P8)

82
Q

When do you give Rotateq?

A

orally at 2, 4, and 6 months

83
Q

What is Rotarix?

A

live, attenuated human-derived monovalent (G1, P8)

84
Q

When do you give Rotarix?

A

orally in 2 doses starting at 6 weeks

85
Q

What is the other option for rotavirus protection?

A

new aerosol (intranasal) that is grown in tobacco plants

GI (21 decks)

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