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Microbiology > GI > Flashcards

GI Flashcards

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Biology 101 flashcards
1
Q

Evaluating GI infections/food poisoning

A
  • history and physical
  • travel history
  • recreational activities
  • duration of symptoms
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2
Q

Duration of GI symptoms

A
  • acute: < 14 days
  • persistant: < 30 days
  • chronic: > 30 days
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3
Q

GI anatomic considerations

A
  • esophagus to stomach to small intestine to large intestine
  • pH of stomach can withstand most bacteria
  • peristalsis of small intestine inhibits adherence
  • colon flora and IgA compete with pathogens
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4
Q

GI risk factors

A
  • number of ingested organisms
  • achlorhydia
  • reduction in normal flora due to antibiotics
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5
Q

Traveler’s diarrhea

A

Enterotoxigenic E. coli

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6
Q

Parasitic infections

A

Giardia, Entamoeba

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7
Q

Antibiotic-associated diarrhea

A

C. difficile

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8
Q

Practical diagnosis

A
  • History (food ingestion, travel, activities)
  • Duration of illness
  • Medications
  • Underlying conditions
  • Physical exam (state of hydration, exam of abdomen)
  • Laboratory studies
  • Fecal exam
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9
Q

Direct fecal smear

A
  • Gram stain of smear

- WBC’s indicate invasion, not toxin

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10
Q

Enterotoxin-mediated diarrhea

A
  • rapid onset indicates preformed toxin
  • lack of fever
  • absence of blood or pus
  • large number of watery stools (> 20/day)
  • Enterotoxigenic E. coli, cholera, S. aureus, C. perfringens, Bacillus cereus, viral or parasitic
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11
Q

Diarrhea mediated by invasion of bowel mucosal surface

A
  • fecal leukocytes, RBC’s, fever

- Salmonella, Campy, Shigella, E. coli, Entamoeba

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12
Q

Diarrhea mediated by invasion of full thickness of bowel with lymphatic spread

A
  • S. typhi, Y. enterocolitica
  • presents with constipation
  • fecal leukocytes and RBC’s
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13
Q

Common viral pathogens

A

Rodaviruses, Enteric adenoviruses, calciviruses, astroviruses

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14
Q

Common bacterial pathogens

A

Campy, Salmonella, Shigella, E. coli, Vibrio (parahaemolyticus, cholera, vulnificus), Y. enterocolitica, C. difficile, Listeria monocytogenes, Helicobacter, Aeromonas, Plesiomonas shigelloides, Edwardsiella, Neisseria gonorrhoeae, Chlyamydia, Treponema

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15
Q

Common parasitic pathogens

A

Giardia intestinalis, E. histolytica, Cryptosporidium, Cyclospora, Microsporidia

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16
Q
  • most common cause of diarrheal illness worldwide
  • microaerophilic, Campy BAP, 42C
  • seagull wing appearance, darting motility
  • oxidase +, catalase +
A

Campylobacter jejuni

17
Q
  • contaminated meat, eggs
  • symptoms 6-8 hours after ingestion
  • usually self-limiting
  • indole -, K/A H2S +, oxidase -
  • enteric fever
  • high inoculum required
A

Salmonella typhi

18
Q
  • dysenteriae, flexneri, boydii, sonnei
  • sonnei is most common in US
  • non-motile, oxidase -
  • causes dynsentery
  • low inoculum required
A

Shigella

19
Q
  • infantile diarrhea

- adhesive, mucus in stool (no blood)

A

Enteropathogenic E. coli

20
Q
  • Traveler’s diarrhea
  • due to poor sanitation
  • requires large inoculum
  • releases toxins
A

Enterotoxigenic E. coli

21
Q
  • dysentery with direction invasion/destruction of mucosa
  • similar to Shigella, but higher inoculum
  • watery diarrhea with blood, mucus and WBCs
A

Enteroinvasive E. coli

22
Q
  • rice-water stool
  • large loss of electrolytes
  • associated with epidemics
  • catalase +, oxidase +
  • toxin produced
  • yellow on TCBS
A

Vibrio cholera

23
Q
  • Summer diarrhea in Japan, associated with seafood
  • diarrhea and cramping
  • green on TCBS
A

Vibrio parahaemolyticus

24
Q
  • “lactose positive” species
  • raw or undercooked seafood, wounds
  • green on TCBS
A

Vibrio vulnificus

25
Q
  • grows at 4C, can go septic
  • meat, unpasteurized milk, dairy products
  • CIN agar (target growth)
  • K/A, ODC +, non-motile
  • self-limiting, possible invasion of mesenteric lymph nodes
  • sometimes mistaken for appendicitis
A

Yersinia enterocolitica

26
Q
  • sometimes normally in intestines
  • antibiotic-associated diarrhea
  • pseudomembranous colitis
  • mild to severe disease
A

Clostridium difficile

27
Q
  • deli meat
  • grows at cold temps
  • CAMP +, catalase +, tumbling motility
  • premature labor, spontaneous abortion
A

Listeria monocytogenes

28
Q
  • peptic ulcers
  • stomach cancer
  • urease +, Christensen’s urea medium, urea breath test
  • cinaedi and fennelliae associated with diarrhea
A

Helicobacter pylori

29
Q

STD’s causing GI infections

A
  • cause proctitis with lose stools and pain on defecation

- N. gonorrhoeae, Chlamydia, Treponema

30
Q

Toxic agents of Food Poisoning (chemical)

A
  • scombroid: flushing, headache, crampy abdominal, tissue of fish
  • Ciguatera: red tide toxin buildup in fish, diarrhea, weakness, abdominal pain
  • Tetrodotoxin: puffer fish toxin (death in 50%)
31
Q

GI Infections in ICPs

A
  • AIDS, cancer, transplants patients
  • high risk for opportunistic infections
  • Bacteria: Mycobacteria membrane attack complex
  • Virus: CMV
  • Parasites: Crypto, etc.
32
Q

GI Infection (lab diagnosis)

A
  • fresh specimen is best for culture
  • Direct microscopic exam: look for fecal leukocytes, RBC’s, seagull wing/curved appearance of Campy and Vibrio
  • streak to SBA, MAC, Choc, SMAC, HE, XLD, Campy agar, CIN, TCBS, CCFA
33
Q

HE plate

A
  • Salmonella shows H2S (black colonies)

- Shigella has no H2S

34
Q

SMAC

A

E. coli O157:H7 doesn’t ferment sorbitol

35
Q

Campy agar

A

selective for Campylobacter jejuni

36
Q

CIN agar (cefsulodin- Igrasan-novobiocin)

A

selective for Yersinia enterocolitica (target/bulls-eye growth)

37
Q

TCBS agar

A
  • Vibrio cholera and alginolyticus utilize sucrose (turn yellow)
  • Vibrio vulnificus and parahaemolyticus don’t utilize sucrose
38
Q

CCFA agar

A

selective for C. difficile (pale yellow colonies - fluoresce bright yellow)

39
Q

Diarrhea treatment and prevention

A
  • replenish electrolytes (IV fluids if necessary)
  • antidiarrheal medications (not for invasive diarrhea)
  • antibiotics to treat infection

Microbiology (26 decks)

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