Lecture 10: Enteric Bacteria - Secretory Diarrhea

What are the two types of diarrhea?

Secretory (watery) diarrhea and Bloody diarrhea (dysentery)

What are happens with secretory (watery) diarrhea?

loss of electrolytes and fluids from the small intestine

What are happens with bloody diarrhea (dysentery)?

local tissue damage and inflammation of the intestinal tract

What is the most common cause of diarrhea?

viral gastroenteritis

What is the 2nd most common cause of diarrhea?

bacterial gastroenteritis (usually more severe than viral gastroenteritis)

What is the number of children deaths from diarrhea annually?

>5 million children annually

What are the enteric bacterial pathogens?

-Vibrionaceae

-Enterobacteriaceae

What are some Vibrionaceae organisms?

-Vibrio cholerae

-Campylobacter jejuni

What are some Enterobacteriaceae organisms?

-Pathogenic E. coli

-Shigella flexnery (EIEC)

-Salmonella typhimurium

-Yersinia enterocolitica

What Enterobacteriaceae cause secretory diarrhea?

-ETEC

-EPEC

-EAggEC

-Nontyphoidal Salmonella

-Yersinia enterocolitica

What Vibrionaceae cause secretory diarrhea?

-Vibrio cholerae

-Vibrio parahaemolyticus

-Campylobacter jejuni

What Enterobacteriaceae cause bloody diarrhea?

-EIEC

-EHEC

-Shigella

-Yersinia enterocolitica

What Vibrionaceae cause bloody diarrhea?

-Vibrio parahaemolyticus

-Campylobacter jejuni

What are the main characteristics of Vibrio cholerae?

-Gram(-)

-curve rod

-Facultative anaerobes

*Single polar flagellum

*Positive oxidase

What disease does V. cholerae cause?

Cholera

What environments are associated with V. cholerae?

aquatic environments

What are associated with V. cholerae?

algae and marine invertebrates

Vibrio cholerae serotypes on basis of O antigens

O1 and O139 strains

Which serotype of V. cholerae is more virulent?

O1 strains (Classic, El Tor biovar)

How is cholera is acquired?

Ingestion of contaminated water or seafood

What are the clinical symptoms of cholera?

-watery diarrhea, vomiting begins 2-3 days after ingestion of bacteria

-followed by dehydration, renal failure

What characterizes cholera?

"rice water" stool

What's the mortality rate for cholera?

60% in untreated patients

How many major pandemics are associated with cholera?

Seven major pandemics since 1817

What are the virulence factors of Vibrio cholerae?

-polar flagellum

-Tcp pili

-Cholera toxin (A-B type cholera)

-Capsule (in O139 strains)

How is cholera treated?

rehydration and antibiotics (occasionally to reduce toxin production)

How can cholera be prevented?

good hygiene and clean water

Who first identified E. coli and when?

Theodor Escherich in 1885

What are the characteristics of E. coli?

-Gram(-)

-rod

-Facultative anaerobes

-Oxidase negative

-Motile

-peritrichous flagella

What are the reservoirs for E. coli?

humans, animals

What are the Enteric pathogenic E. coli strains that cause watery diarrhea?

-Enterotoxigenic E. coli (ETEC)

-Enteropathogenic (EPEC)

-Enteroaggregative (EAggEC)

What are the Enteric pathogenic E. coli strains that cause bloody diarrhea?

-Enteroinvasive (EIEC)

-Enterohemorrhagic (EHEC)

Which pathogenic E. coli strains do not enter cells?

-EPEC

-EHEC

-ETEC

-EAggEC

Which pathogenic E. coli strains enter cells?

-EIEC

-UPEC

-SEPEC

-MENEC

Which E. coli strain cause similar symptoms to cholera?

Enterotoxigenic E. coli (ETEC)

What does Enterotoxigenic E. coli (ETEC) cause?

Traveler's diarrhea (mostly in developing countries)

How many Traveler's diarrhea cases per year?

650 million cases/year

What is usually contaminated by ETEC?

water and fresh vegetable

What virulence factors are associated with ETEC?

Enterotoxins (2 heat-labile, 2 heat-stable)

Adhesins

What are the 2 heat-labile enterotoxins produced by ETEC?

LT-I

LT-II

What other toxin is LT-I similar to and what kind of toxin is it?

Cholera toxin (A-B toxin)

Which ETEC toxin is similar to Cholera toxin?

LT-I enterotoxin

What kind of adhesins do ETEC produce?

Type I adhesins

How long is the incubation time for Traveler's diarrhea?

1-2 days

How long does Traveler's diarrhea persist?

4 days

What are the common symptoms for Traveler's diarrhea?

-similar to cholera but milder

-watery diarrhea and abdominal cramps

Which E. coli strain cause diarrhea in infants and small children?

Enteropathogenic E. coli (EPEC)

Which E. coli strain was first associated with diarrheal diseases?

Enteropathogenic E. coli (EPEC)

What toxins do EPEC produce?

None

What are the virulence factors of EPEC?

-Adhesins: intimin, pili (BfpA)

-Type III secretion system-Tir receptor

What adhesins are produced by EPEC?

-Intimin

-pili (BfpA)

Pathogenesis of EPEC

-EPEC attaches to intestinal epithelial cells via BfpA

-Type III secretion of Tir

What characterizes EPEC-mediated diarrhea?

microvilli destruction in the small intestine that leads to malabsorption

What does Enteroaggregative E. coli (EAggEC) cause?

persistent diarrhea in children and adults (in both developed and developing countries)

What is the main characteristic of EAggEC?

Bacteria aggregate and form a biofilm on the epithelium of the small intestine

What are the virulence factors produced by EAggEC?

enterotoxin and hemolysin

What are the symptoms of EAggEC-mediated diarrhea?

persistent watery diarrhea with vomiting, low grade fever, dehydration

What is the treatment for EAggEC-mediated diarrhea?

oral rehydration therapy

What are some preventive measures for EAggEC-mediated diarrhea?

No vaccines available

Good hygiene

Only drink safe water

Cholera is usually treated with _____.

water containing salt and glucose