L18, 19 : Gram Negative bacteria I Flashcards
lactose fermenting enterobacteria:
late lactose fermenting enterobaceteria:
non-lactose fermenting enterobacteria:
escherichia , klebshella
shigella sonnei
shigella , salmonella
what type of enterobacteria are part of the normal flora in GIT ?
lactose fermenting ones
what types of enterobacteria are intestinal pathogens ?
non-lactose fermenting ones
E.coli properties ? :
gram test :
indole test :
lactose fermenting ?:
gram negative
indole test positive
lactose fermenting yes .
what is the virulent function of LPS surface O Ag on E.coli bacteria ?
endotoxic activity , protects from phagocytosis
which antigen is the flagellar antigen on E.coil?
H- antigen
which surface antigen is the colonization factor?
Fimbriae
describe the action of heat liable toxin of E.coli .
activates adenyl cyclase , which increases Cyclic AMP , which increases secretions of Na , Cl and water from cell
describe the action of heat stable toxin of E.coli .
activates guanyl cyclase , which increases Cyclic GMP , which inhibits ionic uptake in intestinal cells –>osmotic water loss from cells
which toxin of E.coli is ‘shigella-like’, and in what way ?
Verocytotoxin , which inhibits protein synthesis just like shigella toxins , leading to cell death
which type of E.coli induces diarrhea that mostly affects infants , is non-toxigenic and non invasive ?
Enteropathogenic E.coli
E.coli inducing travelers diarrhea that is non invasive but toxigenic :
enterotoxigenic E.coli ( resembles cholera )
E.coli inducing bloody diarrhea (dysentery) that is similar to that of shigella :
enteroinvasive E.coli
enterohemorrhagic E.coli produces which toxin ? and what are its effects on the body ?
verocytotoxin (shigella like toxin )
-Hemorrhagic colitis
-hemolytic uremic syndrome (renal failure , hemolytic anemia , thrombocytopenia )
hemolytic uremic syndrome is a complication of which bacterial infection ? and what does it entail ?
enterhemorrhagic E.coli
renal failure , thrombocytopenia , hemolytic anemia
what is a source of enterohemorrhagic E.coli?
improperly processed beef
which type of E.coli infection has a stacked brink appearance and causes persistent diarrhea in infants in developing countries ?
enteroaggregative E.coli
Klebsiella pnumoniae :
gram test ?
indole test ?
lactose fermenting ?
gram negative coccobacilli
indole negative
mucoid lactase fermenting
capsulated
which bacterial infection produces currant jelly like sputum ?
Klebsiella pnumoniae
what bacterial infections are most related to hospitalization ?
enterobacilli and serratia
serratia :
gram test:
lactose fermenting :
pigment description :
gram negative
lactose fermenting
non-diffusible red pigment
in what aerobic conditions do salmonella and shigella spp. grow ?
facultatively anaerobic (they posses fimbriae(colonizing factor))
what clinical infections can salmonella spp. cause ?
-enteric fever / typhoid : S.typhi / S. paratyphi A,B ,C
-Food poisoning / acute gastroenteritis : serotypes of S.enterica
-septicemia : S. enterica serotype choleraesuis ( also involved in metastatic infections such as osteomylitis )
where is salmonella commonly persistent in the body ?
gall bladder
where do typhoid and other enteric fever begin?
they begin in the small intestine
chronic carrier state :
persistence of salmonella in stool ( gall bladder ) or urine ( kidney ) for more than one year
what does shigella cause ?
bacillary dysentery
Shigella dysenteriae is an example of :
Group A shigella spp.
how is shigella transmitted?
through feco-oral route
how does shigella toxin function?
by inhibiting protein synthesis
what does shigella toxin cause >?
dysentery and hemolytic uremic syndrome
it also acts as a neurotoxin
Which bacteria shows red colonies with black centers and no H2S ?
shigella
what diseases does proteus infection cause ?
UTI
pneumonia
wound infections
septicemia
what property does proteus have that makes it easier for the bacteria to invade the urinary tract ?
vigorous motility
what enzyme does proteus produce and what is that enzymes action?
urease , which breaks down urea in urine to form ammonia –> rasies pH of urine –> formation of stones ( calculi) called struvite stones which manifests as staghorn calculi in renal pelvis
alkaline urine also favors growth of bacteria
describe the growth of proteus on blood agar;
swarming growth
what colonies does proteus form on MacConkey’s agar ?
non-lactose fermenting
what conditions do campylobacter jejuni bacteria grow best under ?
micro-aerophillic and 42 degrees
what does campylobacter jejuni cause?
enterocolitis
what bacterial infection is associated with guillain-barre syndrome , reactive arthritis , and reiters syndrome ?
campylobacter jejuni
what are the sources of campylobacter jejuni?
raw/ undercooked meat
unpasturized dairy products
contaminated water
contact with cat or dog feces
H. pylori :
gram test :
urease test :
gram negative curved or spiral rods that are motile and strongly urease positive
what diseases does H.pylori cause ?
gastritis and peptic ulcer
gastric carcinoma
MALT lymphoma
which organism has darting motility
vibro cholerae
what aerobic conditions are needed for vibrio cholerae to grow ?
strongly aerobic
how is vibrio cholerae transmitted?
through food and water contaminated by feces of carrier
what enrichment media does vibro cholera grow in ?
alkaline peptone water
what selective media does vibriocholera grow in ?
TCBS
