Enteric bacteria- noninflammatory diarrhea Flashcards
1
Q
bacterial causes of non-inflammatory diarrhea?
A
- (ETEC) eneterotoxigenic E coli
- (EPEC) enteropathogenic E. coli
- (EAEC) Enteroaggregative Ecoli
- Vibrio cholera
- vibrio parahemolyticus
- vibrio vulnificus
- S. aureus
Bacillus cereus
2
Q
ETEC (enterotoxigenic E coli) general characteristics
A
- contaminated food/water
- major cause of traveler’s diarrhea
3
Q
clinical presentation of ETEC?
A
- Watery diarrhea, mild to severe range
- duration 1-5 days
4
Q
pathogenesis of ETEC?
A
- 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
5
Q
EPEC (enteropathogenic E coli) general characteristics
A
- 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
6
Q
EAEC (enteroaggregative Ecoli) gen characteristics
A
- 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.
7
Q
what are some other less known e coli infections?
A
- 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)
8
Q
General characteristics of vibrio
A
curved (comma shaped) gram - rods
- motile, polar flagella
- oxidase positive
- found in saltwater commonly, disease in warm months
9
Q
vibrio cholerae gen characteristics
A
- 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
10
Q
which vibrio cholerae serogroups are responsible for epidemic and pandemic cholera?
A
O1 and O139 are responsible for epidemic and pandemic cholera
- o1 serogroup divided into 2 biotypes- e1 tor and classic
11
Q
vibrio cholera pathogenesis
A
= 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
12
Q
clinical presentaiton of vibrio cholera?
A
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
13
Q
diagnosis of Vibrio cholera?
A
- 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)
14
Q
Tx of vibrio cholera?
A
- 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.
15
Q
prevention of vibrio cholera?
A
- clean water supply, appropriate sanitation
- WHO recommends oral cholera vaccine in cholera control programs in endemic areas.
