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Compendium Microbiology > Infectious diarrhea > Flashcards

Infectious diarrhea Flashcards

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1
Q

Differential diagnosis of organisms causing acute diarrhea

  • viral
  • bacterial
  • protozoa
A
  • Viral
    • Norovirus: Calicivirus, norwalk
    • Rotavirus
    • Enteric adenovirus
  • Bacterial
    • Shigella
    • Salmonella
    • Campylobacter
    • E. coli
    • Vibrio
  • Protozoa
    • Entamoeba
    • Giardia
    • Cryptosporidium
    • Isospora
    • Cyclospora
    • Microsporidia
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2
Q

Symptoms of viral diarrhea

A
  • mild fever
  • vomiting
  • mild pain
  • no neutrophils in stool exudate
  • minimal blood
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3
Q

Inflammatory diarrhea symptoms/labs

A
  • blood
  • fever
  • severe abdominal pain
  • tenesmus
  • neutrophils in stool
  • blood without fecal neutrophils could be EHEC or amebiasis
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4
Q

Bacteria causing non-inflammatory diarrhea

A
  • Vibrio - rice water stool (flecks of mucus); serogroups O1-O139 (O1 and O139 most responsible for epidemic cholera)
  • E. coli (ETEC-produces cholera-like toxin, EPEC)
  • S. aureus
  • B. cereus
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5
Q

Bacterial organisms causing inflammatory diarrhea

A
  1. C. difficile
  2. salmonella
  3. shigella
  4. campylobacter
  5. EHEC
  6. aeromonas
  7. yersinia
  8. vibrio (non cholera)
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6
Q

Causes of diarrhea in South and Central America and the Far East

A

South and Central America

  • E. coli

Far East:

  1. campylobacter
  2. shigella
  3. salmonella
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7
Q

E. coli and diarrhea

  • transmission
  • labs
  • symptoms
A

Transmission

  • milk
  • beef
  • vegetables
  • fruit

Symptoms may be inflammatory or non-inflammatory depending on strain

HUS: thrombocytopenia, renal failure, MAHA,

Labs:

  • O157:H7 is clear on Sorbitol-Macconkey agar (does not ferment sorbitol) and no fecal leukocytes
  • ELISA for shiga toxin
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8
Q

Does Enteroinvasive E. coli produce shiga toxin?

A

Does not produce shiga toxin

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9
Q

Salmonellae morbidity derives from

A

Bacteremia for potential of seeding

  • Bones
  • Joints
  • Vascular walls
  • Heart
  • Brain

Young, old, those with prosthetic devices, and immunocompromised at greatest risk (e.g., HIV, sickle cell, diabetes)

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10
Q

Campylobacter jejuni

A

Most common cause of bacterial enteritis in the US

Most common cause of Guillain-Barre syndrome

Reactive arthropathy in people with HLA-B27

Also causes Immunoproliferative small intestinal disease

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11
Q

Clostridium perfringens

A
  • Spores found within food that is inadequately cooked; also in soil and germinate in wounds
  • Sporulation/enterotoxin production produce vomiting and watery diarrhea that may present within 8 hours of consumption
  • Gas gangrene and cellulitis also occur
  • alpha toxin (lecithinase) detected by Nagler test
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12
Q

Clostridium difficile

  • disease
  • strains
  • tests
  • treatment
A
  • Most common abx (clindamycin) associated diarrhea - pseudomembranous colitis
  • BI/NAP1/027 strain more virulent; related to deletion of tcdC gene leading to increased toxin A&B production
  • Tests
    • Culture may give misleading result because hospitalized patients are often colonized
    • Must detect the toxin produced - cytotoxic assay
    • ELISA for toxin is not as sensitive
    • PCR for toxin genes (tcdA for toxin A, tcdB for toxin B and tcdC for toxin A/B regulator) - most sensitive and specific
  • Avoid treating with medication
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13
Q

Klebsiella oxytoca

A

antibiotic associated ischemic/hemorrhagic colitis

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14
Q

Shigella transmission

A

foodborne or person-person or fly transmitted

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15
Q

Stool microscopy for Entamoeba histolytica

  • sensitivity
  • differential
  • other tests
A

50% sensitivity

E. dispar looks morphologically identical to histolytica

(Stool EIA has very high sensitivity and specificity)

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16
Q

Laboratory approach to diarrhea

A

Stool microscopy has 2 purposes:

  1. determine whether leukocytes are present
  2. look for ova and parasites

Assays for stool lactoferrin (product of neutrophils) can substitute for a microscopic search for leukocytes

ELISA can substitute for stool O and P examination

Culture

17
Q

Routine stool culture can isolate

A

Routine stool culture can isolate:

salmonella

shigella

E. coli

campylobacter

yersinia enterocolitica

vibrio

18
Q

Testing for E coli 0157:H7 and C diff

A

Testing for E. coli O157:H7 is dones by culture, EIA, PCR

EIA or PCR also done for C. diff

19
Q

Most common causes of infectious diarrhea

A

Viruses account for most, especially noroviruses

E coli accounts for most bacterial infections, which are responsible for 10% of infectious diarrhea cases

Compendium Microbiology (15 decks)

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