IDMM Week 1 PBL Flashcards by Alana Meikle

List the viruses that cause enteric infections

Rotavirus
Enteric adenovirus
Norwalk virus

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What type of enteric infection do viruses cause

self limited infectious diarrhea

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Transmission of rotavirus

children under 6
contaminated water
fecal oral

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Pathogenic features of rotavirus

destroy mature epithelial cells in the middle and upper villi–watery diarrhea is due to MALABSORPTION

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transmission of enteric adenovirus

young children and infants

sporadic

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Pathogenic features of enteric adenovirus

self limited infectious diarrhea

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Norwalk virus transmission

young and old

fecal oral

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Pathogenic features of norwalk virus

epidemic gastroenteritus with diarrhea, nausea, vomiting

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List bacteria that cause enteric infections

enterotoxigenic E. Coli
Campylobacter jejuni
Yersinia enterocolita
Shigella
Enteropathogenic E. coli 
Salmonella
C. Difficile 
Vibrio cholerae

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Transmission of ETEC

travellers diarrhea

food and water borne

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pathogenic features of ETEC

watery diarrhea

heat labile toxin activates AC–>increases concentration of cAMP

heat stable toxin increases [cGMP]–>resultsin reduced Na+ absorption in villus cells and increased CL- secretion in crypt cells

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Transmission of campylobacter jejuni

mainly kids
contaminated food and water
zoonotic

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Pathogenic features from campylobacter jejuni

gastritis, enterocolitis, septicemia

causes BLOODY diarrhea and FEVER

cholera-like toxins, invasion (leading to inflammation), translocation into lamina propria and mesenteric lymph nodes

Guillain-barre syndrome

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Yersinia enterocolita transmission

mainly kids

contaminated food and water

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Yersinia enterocolita pathogenic features

RUQ pain
BLOODY, mucoid diarrhea
pseudoappendicities, mesenteric adenitis syndrome (Peyer’s patches)
arthritis, ERYTHEMA NODOSUM

HA enterotixin–like E. Coli: invasion into intestinal wall, regional lymph nodes and blood

16-72 hour incubation

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Shigella transmission

fecal oral

contaminated food and water

Shigella pathogenic featuers

DYSENTERY

- invasion, SHIGA TOXIN (causes hemorrhage, inhibits protein synthesis), actin rockets for cell-cell invasion

Enteropathogenic E. Coli transmission

children–nursery school outbreaks

Enteropathogenic E. Coli pathogenic features

watery diarrhea
initial binding is by bundle-forming pilus
binding activates phospholipase C trhough Hp-90–>increase IP3 and Ca2+ which causes actin polymerization immediately beneath the organism–>effacement of microvilli
intimate contact is mediated by a number of proteins )intimin)
organism sits on the flat pedestal created by the altered cytoskeleton
change in cell architecture causes direct damage, excess water, leading to diarrhea
attaching and effacing lesions

salmonella transmission

food and water borne

human and animal reservoirs

salmonella pathogenic features

S. typhi - typhoid fever (including intestinal bleeding)

Gastroenteritis
sepsis

C. difficile transmission

hospital acquired

antibiotic associated

C. difficile pathogenic features

pseudomembrane
enterotoxin–disrupts membrane integrity
cytotoxin–cells lose filaments and lyse
NON INVASIVE

Vibrio cholerae transmission

pandemic

epidemic

vibrio cholerae pathogenic features

severe watery diarrhea due to cholera toxin

parasites associated with enteric infections

giardia lamblia | entamoeba histolytica

transmission of giardia

travellers diarrhea | contaminated drinking water

pathogenic features of giardia

NO enterotoxins NO invasion IgA proteases, sucker disc to adhere cause diarrhea due to MALABSORPTION FROTHY, FATTY stool

transmission of entamoeba histolytica

large reservoir of asymptomatic carriers fecal oral sexual transmission (anal) contaminated food and water

entamoeba histolytica pathogenic features

- BLOODY diarrhea - FEVER - intestinal pain attach to colonic epithelium, lyse colonic epithelial cells, invade bowel wall contain cysteine proteases, channel forming protein for BORING HOLES into plasma membranes

Methods for parasite detection

special formalin preparation | O&P

what tests do you need special requests for?

O&P viruses non-routine bacteria (i.e C. diff and shiga toxin)

Do you use gram staining in most GI infection diagnosis?

No because already a large amount of bacteria in GI under normal circumstances

Why might antibiotics be contraindicated in some enteric infections?

they may lyse the bacteria and release large amounts of endotoxin or exotoxin which exacerbates the symptoms ie with EHEC

Which enteric infections are indicated for antibiotics?

Shigellosis Typhoid fever Cholera

List infection control measures to prevent the spread of enteric pathogens to others

- adequate hand washing - proper disposal of fecal matter - maintain a clean water supply - stay at home if sick - dont share foodstuffs - dont share dishware and eating utensils - wash and cook foodstuffs thoroughly - proper transport and storage of food

Public health measures taken against food-borne illness

- food safe education program - ongoing surveillance programs - mandatory reporting programs (shigella, e. coli, listeria, clostridium botulinum, salmonella)

What is the public health investigation that follows the outbreak of a food-borne illess

1. initial assessment--ID causative agent, investigate its source 2. risk assessment--determine resources required 3. public notices--recall product if necessary--prevent future outbreak 4. post-outbreak education and establishment of new guidelines if required