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Microbiology > Diarrhea > Flashcards

Diarrhea Flashcards

1
Q

• Acute watery diarrhea is main feature of…

A

viral gastroenteritis

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2
Q

two main causes of viral gastroenteritis?

A

norovirus, rotavirus

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3
Q

tx for viral gastroenteritis

A

fluids

no abx

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4
Q

which two viral gastroenteritis causes are part of the calciviridae family?

A

norovirus and sapovirus

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5
Q

How is norovirus diagnosed?

A

RT-qPCR Assay (sensitive and specific)

ELISA (outbreak only)

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6
Q

how is rotavirus diagnosed?

A

RT-qPCR Assay (sensitive and specific)

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7
Q

Which bacterial family has the following morphology?

Aerobic, facultative anaerobic
Gram negative rods

A

enterobacteriaceae

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8
Q

These are four characteristics of…
• Most ferment carbohydrates to lactic acid

  • Flagella (H antigen)
  • Capsule (K or Vi)
  • LPS (O antigen)
A

enterobacteriaceae

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9
Q

Three important species of enterobacteriaceae

A

salmonella, shigella, e. coli

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10
Q

Most members of enterobacteriaceae are motile with what type of flagella?

A

peritrichous

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11
Q

is shigella motile?

A

no

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12
Q

enterobacteriaceae typically have what two virulence factors?

A

endotoxin

capsule

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13
Q

enterobacteriaceae endotoxin is a __________ component of LPS, it can lead to septic shock

A

Lipid A

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14
Q

This mechanism is widely used by gram - bacteria like enterobacteriaceae that can “inject” material into host cell to alter protein expression

A

T3SS (type 3 secretion system)

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15
Q

important species of salmonella that can infect humans…

A

s. enterica

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16
Q

Primary source of salmonella transmission?

A

ingestion of contaminated food/water

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17
Q

Secondary source of salmonella transmission

A

animals

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18
Q

typing of salmonella depends on what two antigens?

A

flagellar H antigen

LPS O antigen

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19
Q

What percent of patients with salmonella gastroenteritis develop bacteremia?

A

5%

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20
Q

This serovar of salmonella is a generalist that infects a variety of hosts causing self-limiting gastroenteritis

A

S. typhimurium

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21
Q

This is the most common clinical isolate of salmonella enterica…

A

S. enterica serovar enteritidis

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22
Q

What type of T3SS is present with salmonella?

A

SPI1

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23
Q

Does E. coli have SPI-1?

A

no

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24
Q

Salmonella leads to what type of changes in epithelial cells?

A

actin and cytoskeletal changes

engulfment of bacterium

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25
Q

Salmonella transits the epithelial cells to and replicates inside _______ to gain access to systemic sites…

A

macrophages

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26
Q

What are three clinically relevant strains of E. coli?

A

ETEC: enterotoxigenic

EHEC: enterohemorrhagic

EIEC: enteroinvasive

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27
Q

Which type of e. coli?

watery diarrhea/intestinal cramps. Travelers diarrhea

1-2 days post-exposure
lasts 3-5 days

A

ETEC

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28
Q

What are two ETEC virulence factors?

A

LT1 - heat labile toxin

STb - heat stabl toxin

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29
Q

Which ETEC toxin activates adenylate cyclase leading to increased cAMP and Cl- into the intestinal lumen?

A

LT1 - heat labile

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30
Q

Which ETEC toxin binds guanylate cyclase leading to increased cGMP?

A

STb - heat stable

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31
Q

This type of e. coli:

  • common foodborne illness
  • also called STEC (shiga toxin producing E. Coli)
  • O157:H7
  • cattle reservior
A

EHEC

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32
Q

Stx binds to what receptor present on human intestines?

A

globotriaosylceramide receptor

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33
Q

What type of toxin is Stx toxin, stopping protein synthesis and cytokine production?

A

A-B toxin

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34
Q

Stx is not released in an T3SS… so how is the toxin released?

A

lysogenic bacteriophage lysis

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35
Q

What are two virulence factors present with EHEC?

A

intimin (adhesin)

Tir (cytoskeletal effects)

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36
Q

This type of e. coli:

  • profuse, bloody diarrhea, dysentery
  • 12 to 72 hour incubation period
  • no flagella, no adherence factors
A

EIEC

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37
Q

EIEC is basically the same as…

A

shigella

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38
Q

what differentiates shigella from other pathogenic e. coli?

A

lac -

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39
Q

What is the most common shigella type, and what is the most virulent?

A

MC: S. sonnei

most virulent: S. dysenteriae

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40
Q

What pathogen?

Can range from mild watery diarrhea to severe dysentery with blood and mucus

1 to 3 day incubation

A

Shigella

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41
Q

What is the initial feature of shigella associated with toxin?

A

watery diarrhea

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42
Q

How does shigella leave the gut?

A

Macrophage cells or dendritic cells engulfment

43
Q

Shiga toxins are produced by which type only, and are encoded by…

A

S. dysenteriae

encoded by Stx phage

44
Q

Which shiga toxin?

very potent
identical to shiga-like toxin on O157:H7

A

Shiga toxin 1

45
Q

Shiga toxin 2 is the same as shiga toxin 1 except 2 changes…

A

structure, immunogenic

46
Q

What causes dysentery with shigella infection?

47
Q

Which two toxins are carried by other shigella species, but are generally less severe…

A

shet1 and shet2

48
Q

What is the route of infx for shigella?

A

fecal-oral

49
Q

how many shigella cells can cause disease?

50
Q

Which bacterial causes of diarrhea are G- and lac-

A

shigella, salmonella

51
Q

Which bacterial cause of diarrhea produces H2S on HE/TSI or SS Agar

A

salmonella

52
Q

What type of media is used to identify diarrhea cause?

A

maconkey agar

53
Q

Which pathogen?

Lac+, H2S-

54
Q

Which pathogen?

Lac-, H2S+

A

Salmonella

55
Q

Which pathogen?

Lac-, H2S-

56
Q

How do you treat shigella, salmonella, e. coli? Why no abx?

A

supportive care

abx prolong infx

57
Q

5% of salmonella is resistant to how many drugs?

58
Q

What can cause D+ HUS from shigella and e. coli?

59
Q

What pathogen?

G- curved rod

acid sensitive, large numbers must be ingested

A

Vibrio cholerae

60
Q

What toxin?

A-B toxin

causes high cAMP, Cl- secretion

Sodium, water follow Cl- into lumen causing diarrhea

A

Cholera toxin

61
Q

What disease?

profuse watery diarrhea

enormous bacterial load

severe dehydration, organ failure, death

62
Q

How is cholera diagnosed?

63
Q

How is cholera treated?

A

oral rehydration

64
Q

when are abx used with cholera?

A

severe cases

65
Q

What disease?

• Diarrhea: loose, watery stools for
several days
• Fever
• Nausea
• Colitis, pseudomembranous colitis
66
Q

What pathogen?

G+ obligate anaerobe

endospore forming

A & B toxins that disrupt actin and cause pseudomembranes

67
Q

What patients primarily get infected by c. diff?

A

hospitalized on abx

68
Q

The below are risk factors for…

65 and older who take antibiotics and receive medical care
• Extended hospital and nursing homes stays
• People with weakened immune systems

69
Q

What drug can increase risk for c. diff in hospitalized patients?

70
Q

If possible, what tx should be stopped in order to prevent c. diff?

71
Q

why does c. diff usually recur even after vanco or metronidazole administration?

A

endospores

72
Q

What process reliably kills endospores?

73
Q

This bacteria has the following characteristics:

  • microaerobic (10% co2, 80% N2, 10& o2)
  • G- s-shaped rod
A

campylobacter

74
Q

What is the most common cause of gastroenteritis in the US?

A

C. jejuni (campylobacter)

75
Q

What virulence factor present on campylobacter has the following characteristics?

  • Provides serum resistance
  • Attachment to host cells
  • Invasion of epithelial cells
76
Q

What is the infectious dose of campylobacter?

A

500-1000 cells (low)

77
Q

What pathogen can cause the below?

  • Self-limiting gastroenteritis
  • Diarrhea (sometimes bloody), fever, severe abdominal pain
  • Typically lasts about a week
A

campylobacter

78
Q

What is a rare complication from C. jejuni that causes symmetric weakness over several days, with recovery over months?

A

Guillain Barre

79
Q

Campylobacter LOS resembles _______ which leads to Ab cross reactivity and Guillain Barre

A

neuronal gangliosides

80
Q

The below are methods of diagnosing…

Microscopy (s-shaped rods)

campy antigen detection

cx with TMP

81
Q

Which organism?

  • motile, flagellated spiral shaped
  • Oxidase positive
  • Catalase positive
82
Q

H. pylori produces _____ which allows it to produce ammonia to survive HCl in gastric environment

83
Q

What H. Pylori virulence factor?

-forms pores in host membranes

84
Q

What H. Pylori virulence factor?

higher incidence of gastric cancer…

85
Q

three methods to dx h. pylori…

A

Gastric biopsy + urease test (invasive)

polyclonal Ab detection (easy, inexpensive)

Cx (difficult)

86
Q

is h. pylori treated with abx? what can occur as a result?

A

yes, c. diff risk

87
Q

Which pathogen?

Gastroenteritis
• Septicemia
• Clostridial myonecrosis (Gas gangrene)
• up to 12 toxins

A

clostridium perfringens

88
Q

The following describes pathogenesis of which organism?

• Ingestion of contaminated meat

– Allowing food to cool to below 60°C allows spore germination
– Reheating to 75°C kills enterotoxin

A

c. perfringens

89
Q

Sxs of c. perfringens occur due to…which means what for its incubation?

A

toxins, short incubation (self-limiting)

90
Q

Three important species of bacillus…

A

B. subtilis, B. cereus, B. anthracis

91
Q

What pathogen has the following characteristics?

G+ rod, forms chains

Aerobic, facultative anaerobe

spore forming

92
Q

Bacillus species are responsible for producing what type of compounds used by humans?

A

(antimicrobials, insecticides)

bacitracin
polymyxin B
Bt toxin

93
Q

Bacillus cereus can cause emetic disease and diarrheal disease. What toxin is responsible for each?

A

emetic: heat stable enterotoxin
diarrheal: heat labile enterotoxin (similar to cholera)

94
Q

Emetic disease from bacillus cereus is frequently caused by…

A

Intoxication from eating contaminated rice

95
Q

If disease is toxin mediated, is there fever?

96
Q

What is a common cause of bacillus cereus diarrheal disease?

A

eating contaminated meat/veggies

97
Q

What pathogen?

G+ cocci

Catalase +

A

staphylococcus

98
Q

What pathogen?

non-motile

optimal growth 30-37 C

can grow between 15-40 C

A

Staphylococcus

99
Q

Staph. Gastroenteritis is caused by…

A

staphylococcal superantigens

100
Q

list the Staphylococcal superantigens

A

SEA, SEB, SEC…through SER

101
Q

What is responsible for food poisoning from staph?

A

staphylococcal enterotoxins

102
Q

What are two important characteristics of staphylococcal enterotoxins?

A

heat labile

resistant to gastric enzymes

103
Q

describe the onset of food poisoning by staph

A

4 hours onset

Microbiology (13 decks)

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