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Liz's Microbiology Module 2 > PBL: Gastrointestinal Cultures > Flashcards

PBL: Gastrointestinal Cultures Flashcards

1
Q

Anatomical regions of the GI tract

A
  • Oral cavity
  • Esophagus
  • Stomach (few bacteria b/c of ↓ pH)
  • Small intestine (duodenum, jejunum, ileum)
  • Large intestine
  • Colon (cecum, ascending, transverse, descending)
  • Sigmoid
  • Rectum
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2
Q

List the members of normal adult bowel flora

A

99.9% anaerobes
- Bacteroides fragilis group
- Clostridium spp
- Bifidobacterium spp
- Anaerobic cocci
- Fusobacterium spp
Aerobes
- E. coli
- Other Enterobacteriaceae
- Enterococcus spp

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3
Q

Collection and transport for stool specimens

A
  • Stool in a sterile cup or rectal swab
  • In the absence of preservative, the sample is only viable for an hour after collection time
  • If placed in preservative (Carey-Blair or buffered glycerol) the sample is viable for 48 hours
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4
Q

What preservative is not acceptable for Vibrio cultures?

A

Buffered glycerol

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5
Q

What media must all stool cultures be plated on?

A
  • SBA
  • MAC
  • SMAC
  • HEK
  • Charcoal CAMPY
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6
Q

What media is available upon the physician’s request?

A
  • TCBS

- YSA/CIN

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7
Q

What stool pathogens must be serologically typed after they’re identified in the lab?

A

Shigella and Salmonella

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8
Q

V. cholerae

- Appearance on TCBS

A

Yellow colonies (sucrose fermenter)

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9
Q

V. parahaemolyticus

- Appearance on TCBS

A

Green colonies (non-sucrose fermenters)

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10
Q

Shigella

- Appearance on HEK, MAC

A
  • HEK: green/clear

- MAC: clear

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11
Q

E. coli 0157:H7

- Appearance on SMAC

A

Clear (sorbitol negative)

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12
Q

Salmonella

- Allearance on HEK, MAC

A
  • HEK: black (H2S production)

- MAC: blear

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13
Q

Yersinia

- Media to set up

A

YSA/CIN or MAC

- Incubate at 25°C

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14
Q

C. jejuni

- Media to set up

A

Campy BAP

- ↑ CO2, ↓ O2, 42°C

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15
Q

C. difficile

- Media to set up

A

CCFA

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16
Q

H. pylori

- Tests

A

Biopsy, CLO test

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17
Q

Purpose of serotyping

A
  • Useful in tracking an outbreak to its original source

- Aids in diagnosis and is required before identification is made

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18
Q

What media should serological typing be done on?

A

Sheep BPA

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19
Q

Which stool specimen must be submitted to the IN State Department of Health for confirmation?

A

Salmonella

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20
Q

Clinical signs of dehydration

A
  • Dry or sticky mouth
  • Low urine amount/color change
  • “Skin tenting”
  • Hypotension
  • Sunken eyes
  • Fatigue
  • Rapid heartbeat
  • Abnormal electrolytes
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21
Q

Clinical signs of severe dehydration

A
  • Alteration in mental status
  • Organ dysfunction (e.g., renal failure)
  • Fever (indicates invasive pathogen)
  • Rapid breathing
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22
Q

Two types of pathogenic mechanisms that contribute to organisms’ pathogenesis of GI illness

A
  • Enterotoxin-mediated diarrhea (pre-formed in food)

- Diarrhea-mediated by invasion of bowel mucosal surface (infection)

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23
Q

Pathogens that cause diarrhea-mediated by invasion of bowel mucosal surface

A
  • Shigella
  • Salmonella
  • Campylobacter jejuni
  • Vibrio spp
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24
Q

Which pathogens cause non-bloody, watery stool (no RBCs, no WBCs, no mucus)

A
  • S. aureus
  • C. perfringens
  • B. cereus
  • B. botulinum
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25
Q

Which pathogens cause symptoms w/in minutes to hours (intoxication)?

A
  • S. aureus
  • C. perfringens
  • B. cereus
  • B. botulinum
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26
Q

Which pathogens cause symptoms ≥1 day?

A
  • Shigella
  • Salmonella
  • C. jejuni (2-3 days)
  • Vibrio spp.
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27
Q

What causes peptic ulcers?

A

H. pylori

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28
Q

What causes appendicitis-like illness esp. in children?

A

Y. enterocolitica

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29
Q

What causes HUS?

A

E. coli 0157:H7

30
Q

What causes sepsis?

A

V. vulnificus or S. typhii

- Positive blood culture

31
Q

What causes Guillan-Barre syndrome?

A

C. jejuni

32
Q

What causes pseudomembranous colitis?

A

C. difficile

33
Q

The gallbladder is a carrier state for what?

A

S. typhii

34
Q

GNRs found in GI

A
  • Shigella
  • E. coli
  • Salmonella
  • Y. enterocolitica
  • Vibrio spp. (curved, comma)
  • C. jejuni (curved, S-shaped)
  • P. shigelloides (straight/coccobacillary)
  • Aeromonas spp (straight/coccobacillary)
  • H. pylori (spiral)
35
Q

GPRs found in GI

A
  • Listeria (small)

- C. difficile (large; spores)

36
Q

What does the presence of RBCs in a Wright stain examination indicate?

A

Bleed in intestinal wall

37
Q

What does the absence of RBCs or pus in a Wright stain examination indicate?

A

Toxin-mediated illness → E. coli, V. cholerae, S. aureus, C. perfringens, B. cereus

38
Q

What does the presence of WBCs in a Wright stain examination indicate?

A

Inflammatory diarrhea

39
Q

What does the absence of WBCs in a Wright stain examination indicate?

A

Doesn’t rule out pathogen b/w 10-15% of stools that yield an invasive bacterial pathogen have an absence of fecal leukocytes

40
Q

If there are WBCs and RBCs present in a Wright stain examination, what pathogens may be present?

A
  • Salmonella
  • Shigella
  • Yersinia
  • Campylobacter
  • EIEC
  • Vibrio spp
41
Q

Campylobacter jejuni

  • Source
  • Disease
A
  • Source: food (esp. chicken)

- Disease: Guillen-Barre

42
Q

Salmonella

- Source for gastroenteritis and food poisoning

A
  • Food: contaminated meat, poultry eggs, dairy products, farmed fish and shellfish
  • Animals: turtles, iguanas, chickens
43
Q

Salmonella

- Source for enteric/typhoid fever

A

Ingestion of fecally-contaminated food or water

44
Q

Shigella

- Source

A
  • Infected food or water (esp. salads and sandwiches prepared by hand)
  • Person-to-person contact (daycares)
  • Fecal-oral route (dysentery)
45
Q

E. coli

- Source

A
  • Coming into contact w/ human or animal feces

- Consumption of hamburger meat or unpasteruized milk

46
Q

Vibrio spp

- Source

A

Shellfish, salt water

47
Q

Y. enterocolitica and pseudotuberculosis

  • Source
  • Disease
A
  • Meat, unpasteurized milk and other dairy products, chitterlings (intestines)
  • Appendicitis-like illness esp. in children
48
Q

C. difficile

  • Source
  • Disease
A
  • Antibiotic-associated; nosocomial; normal flora but can be bad
  • Pseudomembranous colitis
49
Q

Listeria monocytogenes

- Source

A

Deli meats, hot dogs, unpasteurized dairy products

50
Q

H. pylori

  • Source
  • Disease
A
  • Fecal-oral or oral-oral routes

- Peptice ulcers

51
Q

Plesiomonas and Aeromonas

  • Source
  • Disease
A
  • Ingestion of contaminated water or raw shellfish
  • Both cause gastroenteritis
  • Oxidase positive
52
Q

Causative agents of toxin-mediated food poisoning (intoxication)

A
  • S. aureus (food handlers)
  • B. cereus (fried rice)
  • C. perfringens (meats, gravy)
  • C. botulinum (homecanned)
53
Q

Non-inflammatory self-limiting condition characterized by rapid onset of water, non-bloody diarrhea w/ NO FEVER

A

ETEC

54
Q

ETEC produces what toxins?

A
  • Heat stable toxin

- Heat labile toxin

55
Q

Helps stimulate the secretion of fluid into the intestinal lumen

A

Heat stable toxin

56
Q

Leads to hypersecretion of both fluids and electrolytes into the intetsinal lumen, causing watery diarrhea

A

Heat labile toxin

57
Q

ETEC

- Patient populations

A
  • 2nd leading cause of death in children < 5 years old, esp. in infants in developing countries
  • Traveler’s diarrhea
58
Q

How does ETEC cause infection?

A

Bacteria colonize mucosal surface of small intestine by using fimbriae to bind to cells of small intestine. Allows for the release of either one or both enterotoxins produced by ETEC bacterial cells

59
Q

Causes a persistant condition of water, non-bloody diarrhea w/ mucus, often accompanied w/ a low-grade fever

A

EPEC

60
Q

How does EPEC cause infection?

A

Serogroups bind to epithelial surface of small intestine using adhesin which causes a change in intestinal cell’s structure through the destruction of microvilli

61
Q

Patient populations affected by EPEC

A
  • Mostly affects infants, w/ diarrheal outbreaks occurring in hospital nurseries and daycare centers
  • Rarely affects adults
62
Q

Highly INVASIVE pathogen closely related to Shigella, which can directly penetrate the intestinal mucosa cells, causing high fever and profuse diarrhea w/ possible blood and mucus

A

EIEC (INVASIVE!)

63
Q

How is EIEC transmitted?

A

Fecal-oral route

64
Q

Patient populations affected by EIEC

A

Can occur in either children or adults

65
Q

Major cause of foodborne illness and often involves watery diarrhea that progresses to bloody

A

EHEC, STEC, VTEC

66
Q

For identification of EHEC, STEC, and VTEC plate it on ____

A

SMAC (negative)

67
Q

Patient populations affected by EHEC, STEC, VTEC

A

Any age, but young children < 5 and the elderly are more likely to develop severe illness or HUS

68
Q

Symptoms of HUS

A
  • Acute renal failure
  • Hemolytic anemia
  • Thrombocytopenia
69
Q

Besides setting up a SMAC plate for identifying E. coli O157:H7, why do we need to set up a shiga toxin test?

A

E. coli O157:H7 produces a verotoxin, which are shiga-like toxins (SMAC +)

70
Q

Who does EAEC cause infection?

A

Adheres to the surface of the intestine, but in a clumped or aggregative manner, which triggers an increase in muus production

71
Q

EAEC

- Patient populations

A

Pediatic population in developing countries as well as travelers

Liz's Microbiology Module 2 (11 decks)

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