Zimmer: Other bacterial gastroenteritis Flashcards by Sarah Carlson

What is shigella spp?

very closely realted to e. coli

invasive

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Shigella sonnei

most shigella caused GI illnesses

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Shigella flexnori

causes bacillary dysentery

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Shigela dysenteriae

rarest but most severe dysentery (invasive and produces toxin)

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How is shigella transmitted?

Mostly bacterium passing from stools or soiled fingers of one person to the mouth of another person (food is NOT interm)

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What are the sxs of a shigella infection?

diarrhea (often bloody)
fever
stomach cramps

Symptoms start 1-2 days following exposure

Usually resolves in 5 to 7 days.

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What is dysentery?

Frequent, small bowel movements with blood and mucus, accompanied by rectal pain and spasms (tenesmus)

Not a synonym for bad diarrhea!

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What is the difference between amebic vs bacillary dysentery?

Amebic- gradual onset, less prostration, chronic

Bacillary/bacterial- sudden, more prostration, ACUTE + fever, chills, pus

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Shigella spp.

Bacteria
Gram (-)
Bacillus
Facultative anaerobe
nonmotile (shigella have no flagella)
Non spore forming
Mainly lactose negative,

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How do you distinguish shigella from closely related e. coli?

lactose negative and non-moptile

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How does shigella cause disease?

Invades>
moves around to diff cells using mphages to travel>
mphages apoptose>
survival of bacterial>
inflammation>
sxs

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What does shigella use to move around?

actin rockets

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How do you normally tx shigella?

Since Shigella is invasive, if not treated it can spread beyond the GI tract and cause complications

Antibiotics for more severe cases, most usually resolve without antibiotics

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What are possible complications of shigella?

HUS

*s. flexnoria can also cause reactive arthritis

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What causes the most severe dysentery?

shigella dysenteriae

Invasive (phage born toxin)>
shiga toxin (verotoxin)>
toxin acts on vascular endothelial cells>
cell death

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What diseases are caused by e. coli?

DUNG

Diarrhea
Urinary tract infection
Neonatal sepsis
Gram-negative sepsis

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E. Coli

Bacteria
Gram (-)
Bacillus
Facultative anaerobe
motile
Non spore forming
Mainly lactose positive
E. coli

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What is one of the first colonizers of the GI tract at birth and is a GI commensal? What changes it from good to bad?

E. coli

The ability to produce a toxin

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What is a shiga toxin producing E. coli strain?

STEC

Also known as VTEC or enterohemorrhagic E. coli (EHEC)

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What causes travelers diarrhea and diarhea in children?

Enterotoxigenic E. coli (ETEC)

What is the mechanism of E. coli ETEC and EHEC strains?

EHEC, like Shigilla toxin.

ETEC, activates adenylate cyclase, end result water into lumen, NO bacterial penetration

What are the sxs of e. coli ETEC and EHEC strains?

profuse watery diarrhea and abdominal cramping>
progress to bloody diarrhea for EHEC
Fever
Nausea with or without vomiting, loss of appetite
Chills

Less common: headache, muscle aches and bloating

Incubation:
1-3 days ETEC,
3-8 for EHEC
Illness typically lasts 3-4 days, less than 10.

What is a complication of e. coli ETEC and EHEC strains?

HUS

How do you tx e. coli ETEC and EHEC strains?

antibiotics are NOT recommended

How do you track outbreaks fo e. coli ETEC and EHEC strains?

commercial PCR and Ab based kits

WHat are e. coli ETEC and EHEC reservoirs?

processed meet unwashed veggies (fecal oral)

What is the primary reservoir for v. cholerae?

water *Mexico, developing world

What serogroups of v. cholerae produce cholear toxin?

serogroups 01 and 0139

What is the mechanism of cholera toxin?

Activates adenylate cyclase >cAMP → increased Na+ absorption, increased Cl- excretion> Water moves into lumen> dehydration and diarrhea

What acute illness is characterized by rice water stools, vomiting, loss of skin elasticity and dry mucous membranes?

cholera

How do you dx cholera?

confirmed only by isolation of the causative organism from the diarrheic stools of infected people. Less reliable methods are available for poor areas where laboratories may not be available

How do you tx cholera?

antibiotic therapy may help for severe cases, rehydration therapy is really the biggest factor in treatment.

What is the source and who are the carriers for S. typhi?

source- untreated water carriers- humans

Who is particularly vulnerable to typhoid fever caused by s. typhi?

travelers *vaccine available (drinking water, unwashed fruits and vegetables, fecal-oral contaminant)

What Life-threatening illness begins in the GI tract and then moves to the bloodstream and can cause high fevers (103-104 °F), weakness and headache, stomach pains, loss of appetite, diarrhea or constipation Sometimes, a rash of flat, rose-colored spots?

S. typhi causing TYPHOID FEVER

What is hte danger of having a s. typhi symptomless carrier?

feces still contain the bacteria, and illness could reoccur

How do you treat typhoid fever?

antibiotics esp to eliminate risk that pt could become carrier

What matters most w/ diarrheal pathogens?

infectious dose

What are low inoculum diarrheal pathogens?

Tens to hundreds of virions/cysts/bacteria will cause disease Examples: Shigella, Giardia, Entamoeba, Norovirus

What are high inoculum diarrheal pathogens?

Tens of thousands or more needed | Examples: Vibrio cholerae, C. perfringens

What is the medium of infection for high inocuum diarrheal pathogens?

Medium of infection is highly contaminated: food that is contaminated then held at permissive temps; grossly contaminated water Secondary cases rare Example: traveler gets cholera from seafood carried to U.S. from Ecuador in luggage

What is the medium of infection for low inoculum diarrheal pathogens?

Medium of infection does not need to be grossly infected, transmission through bodily contact or almost-clean water possible Secondary cases common. Can be spread in day-care centers, families Example: Toddler contracts Cryptosporidosis in wading pool

What bacteria underlies most antibiotic associated diarrhea?

Clostridium difficile Common in hospitalized patients or patients at care facilities Associated with broad spectrum antibiotic use Spread patient to patient

C. Diff

``` bacteria Gram + (matchstick like) bacilli spore-forming obligate anaerobe motile ```

How does c. diff cause diarrhea?

Exotoxins cause cell death, shallow ulcers, pseudomembranes Early lesions superficial May eventually invade> Pseudomembranous colitis

How does c. diff present?

Wide spectrum: asymptomatic to fulminant Diarrhea, pseudomembranous colitis, fulminant colitis Usually: just diarrhea

What is the danger of fulminant diarrhea?

perforation | comes on suddenly and w/ great intensity

How do you dx c. diff?

Stool smear Difficult to culture b/c its an obligate anaerobe

How do you tx c. diff?

Antibiotics (metronidazole, vancomycin) Severe disease: bowel resection New therapy: fecal transplant