Bacterial infections of the GI tract Flashcards
when do botulism symptoms arise?
12 to 26 hours
what are the symptoms of botulism toxicity?
dizziness, dry mouth, blurred or double vision
abdominal pain, vomiting, nausea
progressive paralysis
what is the most common cause of death in botulism toxicity?
respiratory arrest
is there fever in botulism? why or why not?
no
nothing for immune system to respond to - ingestion of toxin
what is the shape of c. botulinum?
rod
does c. botulinum form spores?
yes
is c. botulinum aerobic or anaerobic?
strict anaerobe
what is the pathogenesis of botulism toxin?
A-B toxin
B attaches to specific receptors on motor nerve endings
A portion enters nerve cell
toxin blocks release of Ach, preventing discharge of NT by exocytosis
floppy baby is infection with what organism?
c. botulinum
what is the treatment for c. botulinum?
IV antitoxin
is c. difficile aerobic or anaerobic?
strict anaerobe
is c. difficile gram negative or positive?
positive
does c. difficile form spores?
yes
what is the shape of c. difficile?
rod
is c. botulinum gram negative or positive?
positive
what organism causes antibiotic associated pseudomembrane colitis?
c. difficile
what is the transmission for c. difficile?
GI tract (fecal oral)
what is the pathogenesis of c. difficile?
antibiotics cause disruption of normal flora
c. difficile colonizes and takes over in GI tract
what are the clinical findings of c. difficile?
pseudomembranes
neutrophils found in non-bloody stool
toxic megacolon
how can pseudomembranous colitis be distinguished from antibiotic associated diarrhea?
presence of toxin in stool
what is the treatment for c. difficile?
oral metronidazol or vancomycin
fluid replacement
is shigella dysenteriae gram negative or positive?
gram negative
what is the shape of shigella dysenteriae?
rod
what is the color of shigella on MacConkey agar? why?
colorless
non-lactose fermenting
how can shigella be distinguised from salmonella?
shigella does not produce gas from glucose fermentation
shigella does not produce H2S
shigella are not motile
shigella has what antigens in their cell walls?
O antigens (polysaccharide, LPS)
what is the pathogenesis of shigellosis?
invades mucosa in distal ileum and colon, but do not penetrate further than GI tract (nor do they enter the bloodstream)
what is the incubation period of shigella?
1-4 days
what is the drug of choice for severe cases of shigella in adults?
a fluoroquinilone (ciprofloxacin)
what is the drug of choice for shigella in pediatric patients?
trimethroprim-sulfamethoxazole or azithromycin
why are fluoroquinolones contraindicated in pediatric patients?
tendinitis and tendon rupture (cartilage and joint damage)
salmonella spp. cause what conditions?
enterocolitis
enteric fevers
septicemia
salmonella is gram negative or positive?
negative
what is the shape of salmonella?
rod
does salmonella ferment lactose?
no
does salmonella produce H2S?
yes
what is the pathogenesis of eterocolitis salmonella typhimurium and most salmonella?
invasion into epithelium and subepithelial tissues of small and large intestines
penetration into lamina propria
what is the best host defense for eterocolitis salmonella typhimurium and most salmonella?
gastric acid
what is the pathogenesis of salmonella typhi?
multiply on mononuclear phagocytes of peyers patches
spread to phagocytes of liver, gall bladder, spleen - bacteremia
what is the incubation for salmonellosis?
12-48 hours
rose spots are indicative of what disease?
s. typhi salmonellosis
what procedure could be done to reduce the carrier state of salmonellosis?
cholecystectomy
e. coli is gram negative or positive?
negative
does e. coli ferment lactose?
yes
what is the shape of e. coli?
rod
how is e. coli distinguished from salmonella and shigella?
e. coli ferments lactose
what is characteristic of ETEC infection?
no blood
what is the pathogenesis of ETEC?
one or more adhesins - adheres to intestinal mucosa
what is the pathogenesis of EIEC (enteroinvasive)?
enters and grows in intestinal epithelium, resulting in cell destruction
large intestine involvement
what are the characteristics of stool in EIEC?
blood and pus
where is EPEC usually seen?
hospital nurseries, bottle fed infants in developing countries
what is the pathogenesis of EPEC?
plasmid dependent adhesins cause loss of microvilli at site of attachment
does EHEC penetrate intestinal epithelium?
no
many individuals with EHEC also develop what other condition?
hemolytic uremic system
what is the main clinical feature of hemolytic uremic system?
lysis of RBCs and kidney failure
are PMNs present in the stool of cholera patients?
no
what is the shape of vibrio cholerae?
curved
is vibrio cholerae gram negative or positive?
gram negative
vibrio cholerae can tolerate what types of extreme conditions?
strong alkaline
high salt
what is the pathogenesis of cholera?
AB cholera toxin
B binds host cell on microvilli of epithelial cells
A causes activation of adenylate cyclase which converts ATP to cAMP
what is the shape of c. jejuni?
motile, curved
is c. jejuni gram negative or positive?
negative
severe cases of c. jejuni are treated with what abx?
erythromycin or cipro
is h. pylori gram negative or positive?
negative
what is the shape of h. pylori?
short spiral, flagellated
what is the pathogenesis of h. pylori?
produces urease which creates an alkaline microenvironment by hydrolyzing urea to ammonia
is c. jejuni urease positive or negative?
negative