Micro: Enteric Bacteria

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Which diarrheal diseases are primarliy toxin mediated?: Cholera

ETEC (EHEC)

Yersinia enterocolitis
Enterotoxigenic E. Coli: Symptoms: watery diarrhea, nausea, abdominal cramps, low grade fever

travelers diarrhea and infantile diarrhea
Describe the virulence of ETEC?: Enterotoxin (Cholera like)

LT: heat labile; similar to cholera toxin but milder

ST: heat stabile; causes increase in cGMP

has fimbriae and CFAs for colonization in the Small Intestine
ETEC: What common disease does it cause?: Traveller's diarrhea
Enteroinvasive E. Coli(EIEC): Describe its mode of infection and symptoms.: INVASION of Large intestine epithelium similar to Shigella

causes dysentery w/ fever, abd. cramping, blood and pus in stool
Enteropathogenic E. Coli: What common disease state does it cause?: Infant diarrhea
EPEC: Describe its mode of pathogenecity?: ADHERENCE to enterocytes (Small intestine)

effacement of microvilli

expresses intimin- mediates entry in to cell

bundle forming pilli for attachment
EPEC: Describe pathogenesis: ADHERENCE to sm. intestine enterocytes

EFFACEMENT of microvilli

*inflammatory response may cause ulceration
What strain of EHEC causes disease? Where is it typically found?: the O157:H7 serotype

it is found in cattle, beef products, and fruit and veggies that have been fertilized with tainted manure
What characteristic differentiates EHEC from other strains of E. coli?: Its inability to ferment sorbitol.
Describe the symptoms caused by EHEC. What is its primary pathogenic mehcanism?: hemorrhagic colitis, bloody diarrhea, abd. cramping

HUS - possibly because of specific LPS
What is the pathogenic mechanism of EHEC?: Shiga like TOXIN

Attachment and Effacing of microvilli leading to their death

Large Intestine
Yersinia enterocolitica: clinical presentations?: enterocolitis involving fever, diarrhea, and abdominal pain

nonenteric lymphadenitis may lead to septicemia
Yersinia enterocolitica: pathogenesis?: INVASION of M cells in small intestine

secretion of a toxin similar to E. Coli Heat stable toxin

* resevior is farm animals
T/F: S. typhii has no animal reservoir while S. enteritidis does.: True.
How is E. Coli Diagnosed and treated?: detection is difficult, some labs may serotype

treated with fluid replacement, antibiotics

EHEC strains grow on Sorbitol agar
What are the steps involved in the pathogenesis of S. typhii?: *binds M cells of GI epithelia *endocytosed and transferred to Peyer's patch *replicates intracellularly *passes through basal lamina *taken up by macrophage and spread thru RES
A chronic carrier state is possible with S. typhii. What organ is notorious for sequestering the bacteria?: Gall bladder
EAEC: what is its primary pathogenic mechanism?: ADHERENCE to enterocytes

Heat stabile toxin called EAST that eleveates cGMP

attaching and effacing lesions
What are general characteristics of Enterobacteriaceae?: Gram(-) bacteria that are part of the normal intestinal flora

non spore formers

ferment glucose

Facultive anearobes
What are the 4 genus' of enterics?: enterobacteriaceae, vibrionaceae, pseudomonadaceae, bacteroidaceae
Vibrio Cholera: clinical manifestations?: Classic "rice water" stool diarrhea w/ high fluid output

infxn may be asymptomatic, cause mild diarrhea, or result in a carrier state
Vibrio Cholera: pathogenesis?: polar flagellum (H-ag) - motility

pili- adherance

cholera toxin

*mucinase to digest mucous layers
*NON INVASIVE!
Describe the Cholera toxin?: two A subunits bridged by disulfide bonds and 5 identical B subunits

A1 is active subunits-enters cell upregulates adenyl cyclase --> increased cAMP leading to cause massive efflux of Na= and H20

*regulon family of genes
Vibrio Cholera: Diagnosis?: darkfeild microscope

isolation on thiosulfate-citrate-bile-sucrose(TCBS) agar

agglutination in specific antisera
Vibrio Cholera: Rx?: Rehydration orally

IV Tetracycline
Vibrio Cholera: Immunity?: post infection Abs

gastric acidity

vaccines are KILLED WHOLE CELLS
Vibrio parahemolyticus: marine org, infects shellfish

major cause of FP in Japan and in US from eating raw shellfish

explosive diarrhea (w/o blood or mucous), cramps, nausea, vomiting

*produces a toxin
Vibrio vulnificus: found in salt h2o, infects sun bathers and those ingesting raw shellfish

can cause a fatal bacteremia

immunocompromised, liver diseased and thalassemia increase risk
Campylobacter jejuni: transmission?: transmitted by contaminated milk, H20, poultry
Camplylobacter jejuni: clinical manifestations?: bloody, pus-filled diarrhea, severe ab pain, fever

high pediatric incidence

no1 cause of gastroenteritis in developed world

*assoc. w/Guillan-Barre syndrome
Camplylobacter jejuni: bacterial characteristics?: G- curved rod

microaerophilic

motile

INVASIVE
Helicobacter pylori: clinical manisfestations?: cause of gastritis, PEPTIC and DUODENAL ULCERS

makes a urease theat produces NH3 from urea

cured with Antibiotics
Shigella species: clinical manifestations?: shigellosis- fever, chills, abdominal cramps, tenesmus

blood/ pus/ mucous in stool

can cause convulsions and meningitis in infants

S. dysenteriae cause most severe infections; S.sonnei and S.flexneri most common in US
Shigella species: transmission?: man is primary host

P to P: fecal-oral transmission or by vectors(food, fingers, feces, flies)

associated w/ overcrowding and poor sanitation
Shigella species: Pathogenesis?: invades/ damages mucosa of large intestine, ulceration, and appearance of PMNS --> scarring

invasion genes are on plasmid, involves actin polymerization

non motile

Shiga toxin, INVASION
Shigella species: Describe the Shiga toxin?: A+B toxin (similar to Cholera)

inhibits protein synthesis by inactivating the 60s ribosome

also behaves as neurotoxin

*not essential for virulence
*associated w/HUS
Shigella species: diagnosis?: rectal swab
stool culture

*Shigella IS NOT Normal Flora
Shigella species: Rx and immunity?: rehydration

antibiotic resistance emerging

previous infection only gives short lived immunity, no vaccine
Salmonella gastroenteritis: clinical manifestations?: diarrhea, fever, cramping, nausea, vomiting, headache

onset 24-48 hrs after ingestion

diarrhea has rotten egg smell

blood stream invasion may occur, but disease is usually self limiting
Salmonella gastroenteritis: organisms: S.typhi --> typhoid fever

S.typhimurium - most common causitive org in US

S. enterica
What are the 3 clinical sydromes that can result from infection with Salmonella species?: 1. enteric fever

2. septicemic syndrome

3. gastroenteritis
Salmonella gastroenteritis: transmission?: fecal-oral route

pet turtles

chicken, raw eggs, mayonaise

unpasteurized OJ, apple cider
Salmonella gastroenteritis: pathogenesis?: attachment and invasion of mucosal (M cells) of SMALL INTESTINE, damages tissue

may produce a toxin but not major virulence factor

*INVASIONS
Salmonella gastroenteritis: diagnosis?: fecal culture on selctive/differential agar (Salm are lac-)

slide agglutination for serogroups
Salmonella gastroenteritis: Rx and immunity?: flouroquinolones (ciprofloxacin)

antimotility drugs

no vaccine
Enteric Fevers: causitive agents?: S. typhi - typhoid fever, Vi antigen (capsular polysacchride)

S. paratyphi and S.schotmulleri cause milder fevers
Enteric Fevers: clinical manifestations?: intially malaise, headache, anorexia

wk1: gradual stepwise rise in fever, constipation or diarrhea

wk2: rose spots, hi fever, septecemia

wk3: fever remits, may have ulceration and gut perforation --> bloody diarrhea
Enteric Fevers: pathogenesis?: ingested and multiply in small intestine

penetrate mucosa at distal end ileum through M cells at Peyers Patches, move through blood stream --> bacteremia

infection of gall bladder can lead to chronic carrier state or reinfection
Enteric Fevers: Transmission?: S.typhi only infects humans by direct contact or ingesting food contaminated by orgs shed by carrier (Typhoid Mary)
Enteric Fevers: Diagnosis?: isolation of org on agar or serotyping

blood is positive in wk1 of infection

stool is positive after wk1

Widal test
Enteric Fevers: Rx and immunity?: Short course, fluoroquinolones

Abs protects, infection stimulates cellular immunity

Vaccines: killed whole cells, live attenuated, IV injected capsular polysacchride
Septicemic Syndrome: organism and clinical manifestations?: S. cholraesuis

causing spiking fevers w/ frequent seeding to various organs --> abscesses, meningitis, pneumonia, osteomyelitis, endocarditis
General characteristics of Enteric Bacteria: Gram - bacilli

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