Enteric bacteria- noninflammatory diarrhea Flashcards
bacterial causes of non-inflammatory diarrhea?
- (ETEC) eneterotoxigenic E coli
- (EPEC) enteropathogenic E. coli
- (EAEC) Enteroaggregative Ecoli
- Vibrio cholera
- vibrio parahemolyticus
- vibrio vulnificus
- S. aureus
Bacillus cereus
ETEC (enterotoxigenic E coli) general characteristics
- contaminated food/water
- major cause of traveler’s diarrhea
clinical presentation of ETEC?
- Watery diarrhea, mild to severe range
- duration 1-5 days
pathogenesis of ETEC?
- organism produce heat-labile toxin (LT) and heat stable toxin (ST)
- LT similar to cholera toxin. stimulate AC and increase cAMP –> cl secretion from intestinal crypt cells and inhibition of absorption of NaCl at villous tips. secretion of free water into intestinal lumen –> watery diarrhea
- ST activates enterocyte cGMP–> stimulation of cl- secretion and inhibition of NaCl absorption. End result again is secretion of free water into the intestinal lumen and watery diarrhea
EPEC (enteropathogenic E coli) general characteristics
- Most commonly associated with illness among children <6 mo and 2 years of age in developing countries
- profuse watery diarrhea w/ severe vom and dehydration
- org can produce attaching and effacing lesions and forming pedestal like structures (LEE) – no shiga toxins produced
EAEC (enteroaggregative Ecoli) gen characteristics
- cause of diarrhea in children and adults in both developed and developing countries
- also can affect HIV pts in developing countries (and probabs developed countries)
- can cause traveler’s diarrhea
- pathogenesis is not well understood.
what are some other less known e coli infections?
- hospital acquired infections
- neonatal meningitis (Encapsulated strains k1 antigen)
- Uropathogenic E. coli (UPEC)- 90% of UTI cause!! F > M
dx UPEC via bacteria in urine. virulence factor include p fimbriae (PAP) and capsule (k antigen)
General characteristics of vibrio
curved (comma shaped) gram - rods
- motile, polar flagella
- oxidase positive
- found in saltwater commonly, disease in warm months
vibrio cholerae gen characteristics
- transmit through fecally contaminated drinking water, less often food (natural/man-made disaster areas)
- poor sanitation, malnutrition, overcrowding, inadequate medical services
- endemic in Asia, africa, s. america, indian subcontinent
- humans are carriers and environmental reservoirs
- main animal reservoirs: marine shellfish
which vibrio cholerae serogroups are responsible for epidemic and pandemic cholera?
O1 and O139 are responsible for epidemic and pandemic cholera
- o1 serogroup divided into 2 biotypes- e1 tor and classic
vibrio cholera pathogenesis
= colonization of small intestine and secreiton of toxin
- large #’s of bacteria must be ingested for colonization since it is sensitive to stomac acid.
- adhere to cells of brush border of gut and is related to secretion of bacterial enzyme mucinase which dissolves glycoprotein covering over the intestinal cells
- organism multiplies and secretes cholera toxin - AB toxin
- 5B bindign subunits- bind to ganglioside R on the surface of enterocyte
- 1A active subunit, inserted into the cytosol and catalyze addition of stimulation of adenylate cyclase. As a result cAMP overproduction activates cAMP dependent protein kinase which phosphorylates ion transporters in cell membrane –> loss of water and ions from the cell
- watery efflux enters the lumen of the gut and massive watery diarrhea ensues
clinical presentaiton of vibrio cholera?
incubation period 1-3 days
- large vol watery diarrhea (up to 20L/day)
- no RBCs or WBCs in stool
- stool often called rice water stools bc of watery stools with flecks of mucous. often has fishy odor. Large number of orgs in the stool
- vomiting
- abd pain absent
- dehydration is common - loss of fluids and electrolytes lead to cardiac and renal failure. acidosis and hypokalemia also occur as a result of loss of bicarb and K in stool
diagnosis of Vibrio cholera?
- most tiems diagnosed via clinical suspiction
- organisms can be isolated from stool sing selective media like TCBS agar, TTGA aor macconkey agar (colonies will be colorless)
Tx of vibrio cholera?
- aggressive volume repletion
- ab adjunctive therapy for pts with cholera and moderate severe volume depletion: tetracyine, erythro, azithro, cipro
- WHO recommend using a reduced osmolar ORS which has been demonstrated to decrease stool output, vomiting, and the need for supplemental IV fluids.
prevention of vibrio cholera?
- clean water supply, appropriate sanitation
- WHO recommends oral cholera vaccine in cholera control programs in endemic areas.
vibrio parahemolyticus general characteristics
-marine organism transmit through ingesting raw or undercooked seafood esp shellfish/oysters
**- **major cause of diarrhea in japan
- relative rarare in US but can be seen in gulf and pacific coast in warm months
clinical presentation of v. parahaemolyticus?
- incubation period of 1 day
- mild to severe watery diarrhea, n/v, abd cramps, fever
- self limited of about 3 days duration
bacteremia can occur in those with underlying conditions such as liver disease
- wound infections- handling seafood assoicated with
diagnosis and tx of v. parahaemolyticus?
diagnosis- culture
tx- volume repletion. in severe cases ab warranted give doxycyline
vibrio vulnificus general characteristics and clinical presentation?
- marine organism
diarrhea, severe skin and soft tissue infection
**Shellfish handlers who get hand outnds are at risk
- can cause rapidly fatal septicemia in immunocompromised people eating raw shellfish containing org
- pts most at risk are those with underlying liver disease, alcohol abuse, and some other chronic disease like RA and DM
**- bullous skin lesions are characteristics. **
Vibrio vulnificus diagnosis and tx?
diagnosis- culture
tx- doxy + cefotaxime or ceftriaxone
bacillus cereus general characteristics?
- spore forming gram + bacilli
- survice in environment for extended periods of time and withstand extremes of temperature
- survice in food processing environments
**Fried rice important cause of emetic type food poisoning.
- 2 enterotoxin: diarrheal enterotoxin and emetic toxin
Clinical presentation of bacillus cereus?
- diarrheal syndrome: abd cramps, lots of diarrhea, 8-16hrs after ingestion, resolves within 24 hrs. vom uncommon
- emetic syndrome: caused by direct ingestion of the toxin cereulide. abd cramps, n/v. diarrhea occur in 1/3 of people. onset within 1-5 hrs of ingestion, resolve in 6-24 hrs
**RIce dishes–result of cooling fried rice dishes overnight at room temp and then reheating the next day!
S. aureus general characteristics and clinical symptoms
- enterotoxin, heat stable. act as superantigen in GI tract to stimulate IL-1 and IL-2 release
- associated with food consumption prepared by a food handler such as dairy, produce, meats, eggs, and salads (potato salad at picnic)
* food handler contaminates products or food left at room temp and orgs multiply and produce lots of toxin
- symptoms: 1-6 hrs of ingestion w/ nausea/vom/abd cramps. fever and/or diarrhea can occur in minority of pts.
- typically last for 24 hrs or less but can be longer.
