B5.020 - Prework Diarrheal Pathogens Flashcards
name the orgs that cause secretory gastroenteritis
vibrio cholerae
ETEC
Clostridium perfringens
Bacillus cereus
Staph aureus
describe mechanism of secretory gastroenteritis
enterotoxin or bacterial adherance/invasion causes shift in water and electrolyte excretion/adsorption
what orgs cause inflammatory gastroenteritis
shigella
EHEC
Salmonella NOT TYPHI
Vibrio parahaemolyticus
C. diff
campylobacter
mechanism of inflammatory diarrhea
bacterial invasion or cytotoxins cause mucosal damage that leads to inflammation
orgs responsible for invasive gastroenteritis
salmonella typhi
yersinia enterocolitica
mechanism of invasive gastroenteritis
bacteria penetrate the mucosa and invade the reticuloendothelial system
describe vibrio
gram - curved rods
motile
oxidase +
common inhabitants of marine environments
many are halophilic
3 major human vibrio pathogens
v. cholerae
v. parahaemolyticus
v. vulnificus
which vibrio causes gastroenteritis
v. cholerae
which vibrio cause wound infections, septicemia, cellulitis
v. parahaemolyticus
v. vulnificus
what is cholera
profuse, watery diarrhea “ricewater stools”
caused by toxin producing strains of v. cholerae
what serotypes of v. cholerae produce cholera
O1 and O139
epidemiology of cholera
endemic to south asia
8 cholera pandemics in last 200 years
v. cholerae is only vibrio that can grow without salt
what is v. cholerae O1
El Tor
what is O139
Bengal
which pandemic strain made it to Haiti
O1 El Tor
where was the O1 El Tor found after the haiti earth quake
Haiti
Napaleses downstream river of UN camp
DR
MX
Cuba
describe Cholera in the US
Most cases imported
100 documented/yer, 5000 estimated undocumented
associated with consumption of shellfish
describe transmission of cholera
requires high infectious dose of 10^8
person to person is rare
epidemics associated with poor sanitation, usually fecal contamination of wajter supply
sporadic cases often associated with shellfish
virulence factors of cholerae
flagella - necessary to swim toward epithelium
toxin coregulated pili (TCP) - necessary for bacterial attachment to epithelium of small intestine
Cholera toxin (CT) - an AB toxin responsible for symptoms of cholera
describe the pathogenesis of cholera on a micro level
flagellum help the bug swim towards epithelium, it attaches using TCP and then CT uses AB toxin system to insert toxin which blocks GTPase activity of Gs activating cAMP and allowing for electrolyte secretion
clinical manifestations of cholera
incubation period mean 2 days
abrupt onset of diarrhea, abdominal cramps, nausea, vomiting
fever usually absent
diarrhea can range from water to “ricewater” (fluid + mucus + vibrios)
loss of fluid and electrolytes due to cholera leads to what
dehydration
acidosis
hypokalemia
hypovolemic shock
cardiac arrhythmia
renal failure
death in 50-60% untreated pts
spontaneous resolution in 5-7 days
lab dx of cholera
microscopy of stool specimen
culture selective for vibrio - TCBS
agglutination with O group 1 or 139
confirmed case of vibrio requires what
O group 1 or group 139 antigen and CT production
cholera treatment
rehydration tharapy
oral rehydration salts (NaCl, KCl, NaHCO3, glucose)
antibiotics can speed - ceftriaxone, doxycycline, azithro for pregnant, kids
cholera prevention
good public sanitation
Boil it, cook it, peel it or forget it
vaccine - contains killed O1 and rCTB B subunit
(aso prevents ETEC)
describe v. parahaemolyticus epidemiology and what its associated with
common inhabitant of coastal waters
most common in summer months
infections associated with raw or undercooked seafod esp oysters
describe disease from v parahaemolyticus
gastroenteritis similar to mild cholera sometimes with low grade fever
self limiting in 3-5 days
pts with immunodeficiencies or liver disease can be treated with doxy and cetriaxone
wound infections from exposure to sea water
lab culture of v parahaemolyticus
halophilic
TCBS
describe v. vulnificus
similar to v. haemolyticus in distribution/transmission
more likely to cause invasive disease
pts experience fever and chills
more aggressive skin and soft tissue infections
v. vulnificus
who gets v. vulnificus and how is it treated
pts with DM, liver disease or immune dysfunction mroe likely to develop bacteremia
up to 50% fatality rate
treat septic or compromised pts with doxy or 3rd gen ceph
what are aeromonas and plesiomonas
can cause GI disease, wound infections, invasive infections
gram - rod shaped, facultative anaerobes
associated with fresh, brackish water (NOT SALT)
who gest disease from aeromonas and plesiomonas
associated with consumption of contaminated food (fish, shellfish) or water
foreign travel
describe anaerobes
most anaerobic pathogens are aerotolerant meaning they tolerate brief exposure to variable O2 leves, some have SOD and catalase, NADH oxidoreductase (turns O2 to water)
why dont anaerobes grow in oxygen
high redox potention of tissues due to dissolved O2
describe tersinia
gram - non motile, non spore forming
describe where yersinia is found
common cause of enteritis in colder climates
consumption of undercooked pork, chitlins, ubiquitous in soil and pigs
majority in kids under 4
describe yersinia growth
can grow in wide range of temps, 1C-40C
motile at 25, non motile at 37C
describe yersinia diseases
gastroenteritis - 1-10 d incubation, symptoms for 1-2 wks
mesenteric adenitis - mimics acute appendicitis
blood transfusion related - bacteremia and endotoxic shock, due to growth of yersinia in contaminated refrigerated blood
virulence factors of yersinia
Heat stable enterotoxin
Yops - T3SS and effectors, plasmid coated
Invade M cells of Peyers patches
Inv - a chromosomally encoded protein required for invasion of non phagocytic cells
move to mesenteric lymph nodes which can become intensly swollen
intestinal inflammation can lead to bloody diarrhea
treatment and prevention of yersinia
safe food handling
GE is usually self limited and treatment is symptom based and supportive
antibicrobial treatment for sever septicemia
DOC - ceftriaxone
