enterobacteriaceae lec slides

• Gram Negative Bacilli:
• Enteric Gm Neg Bacilli:
– Bacteroides fragilis
– Citrobacter diversus
– Enterobacteriaceae
– Escherichia coli
– Klebsiella Pneumoniae
– Proteus mirabilis
– Salmonella typhi
– Serratia
ENTEROBACTERIACEAE,
VIBRIO, CAMPYLOBACTER
AND HELICOBACTER
Enterobacteriacea
• gastrointestinal diseases
– Escherichia coli
– Salmonella
– Shigella
– Yersinia entercolitica

Enterobacteriaceae
• community acquired
• otherwise healthy people
– Klebsiella pneumoniae
* respiratory diseases
* prominent capsule

– urinary tract infection
– fecal contamination
– E. coli
– Proteus
– urease (degrades urea)
– alkaline urine
– gram negative facultative anaerobic rods
– oxidase negative (no cytochrome oxidase)

Feces
• E. coli
– lactose positive
– not usually identified
– lactose positive sp. common, healthy intestine
• Shigella, Salmonella,Yersinia
– lactose negative
– identified

Diarrhea and Dysentery
Escherichia coli
• E. coli and Shigella
– genetically indistinguishable
– many similarities in diseases
1. Enteropathogenic E. coli
destruction of surface microvilli
• fever
• diarrhea
• vomiting
• nausea
• non-bloody stools
2. Enterotoxigenic E. coli
• diarrhea like cholera
• milder
• travellers diarrhea
3.Enteroinvasive E. coli (EIEC )
• Dysentery
- resembles shigellosis
4. Enterohemorrhagic E. coli
• Enterohemorrhagic E. coliVero toxin
– “shiga-like”

• Hemolysins


Meat
• Hemorrhagic
– bloody, copious diarrhea
– few leukocytes
– afebrile
• hemolytic-uremic syndrome
– hemolytic anemia
– thrombocytopenia (low platelets)
– kidney failure

Treatment -gastrointestinal disease
• fluid replacement
• antibiotics
– not used usually unless systemic
– e.g. hemolytic-uremia syndrome
Shigella
• S. flexneri, S. boydii, S. sonnei, S. dysenteriae
– bacillary dysentery
– shigellosis
• bloody feces
• intestinal pain
• pus

Shigellosis
• within 2-3 days
– epithelial cell damage

Salmonella
• 2000 antigenic "types”
• genetically single species
– S. enterica
• disease category
– S. enteritidis
– many serotypes
– S. cholerae-suis
– S. typhi

Salmonellosis

• S. enteritidis
– the common salmonella infection
– poultry, eggs
– no human reservoir
– Gastroenteritis
• nausea
• vomiting
• non-bloody stool
• self-limiting (2 - 5 days)
• uncomplicated cases (the vast majority)
• antibiotic therapy not useful
S. cholerae-suis
• much less common
• septicemia
• antibiotic therapy essential
Typhoid
• enteric fever
• severest salmonella disease
• Salmonella typhi
• rare in US
• epidemics
– third world
– Europe
* historical

Salmonella typhi
• human reservoir
– carrier state common
• contaminated food
• water supply
• poor sanitary conditions

S. typhi
• Vi (capsular) antigen
– protective

Typhoid -Therapy
• Antibiotics
– essential
• Vaccines
– ineffective

Vibrio cholerae
Vibrios
• Gram negative rods
• comma shaped
• facultative anaerobes
• oxidase positive
• simple nutritional requirements
• readily cultivated
Occurrence -cholera
• third world
• US
– uncommon
* traveler
* ingestion of sea-food
Transmission - V. cholerae
Feces--water
– fresh
– Salt-----
– food
Cholera toxin- Choleragen

• B binds to gangliosides
• provides channel for A
• A catalyses ADP-ribosylation
– regulator complex
– activates adenylate cyclase

Cholera -therapy
• massive secretion of ions/water into
gut lumen
• dehydration and death
• therapy
• fluid replacement
• antibiotic therapy
• vaccination
• partially effective
• not generally used
• international travelers
Vibrio parahemolyticus
• raw sea-food
• grows best in high salt
• not common in US
• diarrhea

CAMPYLOBACTER & HELICOBACTER
• Gram negative rods
• curved or spiral
• genetically related

Campylobacter
C. jejuni
• infects the intestinal tract of animals
– cattle and sheep
– major cause of abortions
Transmission
• milk
• meat products

Isolation - Campylobacter
• microaerophilic
• grows best 42oC

Campylobacter - symptoms
• diarrhea
• malaise
• fever
• abdominal pain
• usually self-limiting
• antibiotics occassionally
• bacteremia
– small minority
Helicobacter pylori
• stomach mucosa
• ulcers
Urease
Important in neutralizing stomach acid
Diagnosis -Helicobacter
• Culture
- urease NH4+ CO2
• mucosal endoscopy NH4
• radioactive CO2 breath
after feeding radioactive urea



Therapy -Helicobacter
• Antibiotics
– cures ulcers
Summary statement
• sanitary measures
– protect the water supply
• food/water borne epidemics
– rare US
– common third world
• zoonotic infections
– contaminated animal products
– less well controlled
– common US and elsewhere
Therapy
• severe diarrhea
– fluid replacement essential

• antibiotic therapy sometimes used in local
infection but always in systemic disease