Enterobacteriaceae - Kirn 4/27/16 Flashcards
enterobacteriaceae
vibrio
campylobacter, heliobacter
enterobacteriaceae
- short, thick rods
- peritrichous flagella
- oxidase negative
vibrio
- curved rods
- polar flagella
- oxidase positive
campylobacter, heliobacter
- curved or spiral shaped
- not closely related to other entero bacteria
epidemiology of enteric bacteria
habitat: intestine
transmission: fecal-oral
- food (and water)
- flies
- feces
- fingers
intestinal defenses
gastric acid
intestinal motility
normal gut flora
IgA mucosal immunity
inflammatory response (phagocytes, complement)
serotyping antigens
H - flagella
O - LPS
K - ‘kapsule’
important bc diff serotypes differ in virulence
3 types of intestinal infections
1. non-inflammatory: bacteria in lumen
2. inflammatory: bacteria invade wall
3. penetrating: bacteria beyond wall
non inflammatory enteritis
watery diarrhea
- no wbc or lactoferrin in feces
no fever
virulence factors: adhesins, exotoxins (
- exotoxins stimulate salt transport from enterocytes into lumen → water follows by osmosis → diarrhea
ex. Vibrio cholerae, toxin-producing E. coli
definition:
EXO vs ENDOtoxins
exotoxins: proteins deliberately secreted by bacteria
endotoxins: LPS on Gram neg bacteria
inflammatory enteritis
diarrhea, often bloody
- wbc or lactoferrin in feces
fever
virulence factors: adhesins, cytotoxins, cell invasion
- bacteria invade enterocytes via type III secretion system and kill hosts
- enterocytes and neutrophils mount local infl response → diarrhea
- exotoxins may have systemic effect
ex. Shigella, Salmonella, Campylobacter, invasive E. Coli
penetrating enteritis
early on: may/may not have diarrhea
- bacteria are in sm intestine
later on: systemic febrile illness
- bacteria have invaded/exited large intestine
virulence factors: adhesins, cell invasion, inhibition/killing of phagocytes
invade intestinal wall, spread…
- to lymph nodes (Yersinia)
- systemically (Salmonella typhi)
extra-intestinal infections
- UTIs
- septicemia, meningitis
- nosocomial infections
- opportunistic infections
UTIs
E. coli is the cause of 80% of uncomplicated cases
- P-fimbrae allow adhesion to urinary tract epi
cystitis: infection of bladder
- urgency
- frequency
- dysuria
tests:
- quantitative culture (need to get quantity bc bacteria always present in urine)
- dipstick test : quick test for neutrophil, bacterial enzymes
pyelonephritis (kidney infection):
septicemia, meningitis
E. coli K1 : neonatal infections
S fimbrae : adhere to endothelium, choroid plexus
K1 capsule : polymer of sialic acid
- not immunogenic; resembles host → doesn’t activate complement
Fe acquisition system that works better than non-pathogenic versions
nosocomial infections
hospital-acquired
- tend to be more drug-resistant than community-acquired infections
examples:
Enterobacter
- resistance mechs: ESBL, carbapenemases
Klebsiella
- resistance mechs: ESBL, carbapenemases, etc
- v encapsulated
- necrotizing pneumonia w bloody CURRANT JELLY-like sputum
Serratia
- red pigment colonies
- often MDR
Pseudomonas aerunginosa
basics
- ubiquitous in environment
- (soil, water, vegetation, biotic/abiotic surfaces)
- found in biofilms: community of many types of bacteria attached to abiotic surfaces via polysacch capsule
- OPPORTUNISTIC
- many virulence factors
- many mechs of antibiotic resistance
Pseudomonas aerunginosa
characteristics
Gram negative rod
polar flagella
obligate oxidizer; no acids from sugars on test media
many isolates produce siderophores (pyoverdin)
smells like grape juice!!!
