Enterobacteriae Flashcards
Enterobacteria general characteristics
- facultative anaerobe
- gram negative
- noncapsulated
- motile
- nitrate reduction
- oxidase negative
- catalase positive
- ferment sugars
- non fastidious
- non spore forming
Components of the cell wall of enterobacteria
Somatic O polysaccharide
Core polysaccharide
Lipid A
Serologic Ags of Enterobacteriae
Somatic O -> strain specific, cross rx between closely related genera
K Antigens -> in the capsule
H Antigens -> in flagella -> heat labile
Motile species of Enterobacteriae are coated with
Peritrichous flagella
Common virulence factors associated with enterobacteria
- endotoxin _> depends on Lipid A component of LPS
- capsule
- antigenic phase variation
- type III Secretion System
- sequestration of growth factors -> siderophores
- resistance to serum killing
- antimicrobial resistance
Dieseases caused by e. Coli
Gastroenteritis, UTIs (produce Hemolysin A), neonatal Meningitids (K1 capsular Antigen), Sepsis
E. Coli gastroenetrotis causing strains
ETEC -> heat stable (ST) and heat labile (LT) enterotoxins
EPEC
EAEC -> shortening of microvilli
STEC -> evolved from EPEC, shiga toxin
EIEC
Species of Salmonella
Salmonella enterica -> Salmonella typhi
Salmonella bongori
Pathogenesis of Salmonella sp.
- endotoxin
- capsule
- ability to invade cells
- replicate intracellulary
- survival in macrophages & spread
- tolerance to acids
- pathogenicity island I and II
- type III secretion system
What is reservoir of salmonella sp.?
Gallbladder
Species of shigella
S. Dysenteria (produces Shiga toxin)
S. Flexneri
S. Sonnei
S. Boydii
Pathogenesis of Shigella
- invade M cells in colon
- Type III secretion
- replicate in cytoplasm
- actin rearrangement
Yersinia species
Y. Pestis _> plague
Y. Enterocolita -> self limiting gastroenteritis
Y. Pseudotuberculosis -> gastroenteritis
Klebsiella characteristics
- nonmotile
- polysaccharide capsule
- resistant to most antibiotic classes
- k. Pneumonia, k. Oxytoca
Whoch enetrobacteria produces Urease, raises urine pH and renal stones?
Proteus
Agar of enterobacter
MacConkey
Cell morphology of Enterobacteriacaea?
Gram negative bacillary or cocobacillary cells
Colonial morphology of Enetrobacteriacea on
- blood agar
- MacConkey agar
- SS agar
Blood Agar: large, dull, dry or mucoid, swarming phenomenon for proteus
MacConkey Agar: lactose fermenter produce red colonies (E. coli), lactose non fermentors produce colorless or transparent colonies (Salmonella)
SS Agar: Salomonella -> colorless colonies with black centers
Shigella -> colorless colonies with no blackening
