Enterobacteriaceae Flashcards
What are 4 major characteristics of all bacteria in the family Enterobacteriaceae?
- negative Gram stain (thin peptidoglycan, hide their cell wall by outer membrane with LPS)
- rods
- catalase positive
- oxidase negative
What are the major 2 groups of Enterobacteriaceae? What bacteria are found in each group?
- LACTOSE FERMENTERS (coliform)
- Citrobacter
- E. coli
- Enterobacter
- Klebsiella - LACTOSE NON-FERMENTERS (pathogenic)
- Salmonella
- Proteus
- Yersinia
- SHigella
How do the members of the CEEK and SPY-Sh compare in lactose fermentation, gas production, and urease tests?
LACTOSE FERMENTATION
- positive = pink on MacConkey = CEEK
- negative = yellow on MacConkey = SPY-Sh
GAS
- CO2 = yellow on TSI = EK
- H2S = black on TSI = CPS
- no gas = red = Y
UREASE
- positive = pink = CKPY
- negative = yellow = ES
What respiration do all Enterobacteriaceae undergo? How do they grow?
facultative anaerobe
non-fastidious and non-spore-forming on bile containing media - MacConkey agar
Almost all Enterobacteriaceae are motile. What are 2 exceptions?
- Klebsiella
- Shigella
lack flagella
What is the primary habitat for Enterobacteriaceae? Where else can they be found?
small and large intestine (commensal of digestive tract)
- GI tract
- mammary glands
- urogenital tract
- respiratory tract
- environment
How are Enterobacteriaceae transmitted? How do they enter and leave hosts? What is one exception?
oral-fecal transmission
ENTRY: oral route by ingestion of contaminated food/feed and water
EXIt: feces, urine, milk, nasal discharge
Y. pestis enters host via flea bites
What are the 5 main opportunistic diseases caused by Enterobacteriaceae?
- diarrhea
- urinary tract infection
- septicemia
- pneumonia
- meningitis
What are the 6 main impacts of Enterobacteriaceae?
- major cause of GI infection (diarrhea, dehydration)
- major cause of liver abscesses
- cause 70% of UTIs
- cause 33% of bacteremia and septicemia
- major cause of meningitis
- major cause of mastitis originating from the environment (Proteus and coliforms)
What is the main way that hosts die due to Enterobacteriaceae?
diarrhea and dehydration—> acid-base and electrolyte disturbance
What are the 3 main surface structures used as virulence factors in Enterobaceriaceae?
- capsule
- flagella, fimbriae, adhesins, invesins
- LPS endotoxin
What 5 things does the lipopolysaccharide on the membrane of Enterobacteriacea cause?
- intestinal adhesion
- colonization
- inflammation
- fever (pyrogenic)
- blood vessel damage —> ischemic necrosis
What are the 2 enzymes used as virulence factors in Enterobacteriaceae? What do they do?
- catalase
- superoxide dismutase
detoxify free radicals
What 3 toxins and secreted substances act as virulence factors in Enterobacteriaceae?
- hemolysins - kill host RBC to make iron available for bacteria
- siderophores/enterobactin - rob iron from host cell
- pathogenic island that codes for type three secretion systems (T3SS)
What are type three secretion systems (T3SS)? In what bacteria are they characteristic?
syringe-like apparatus on the cell wall that can inject bacterial enzymes, toxins, and cytokine inhibitors into host cells
G- ; G+ bacteria lack these
What part of LPS acts as an endotoxin? What does it do? Which part of LPS is variable?
lipid A
- destroy blood vessels
- induce fever (pyrogen)
O antigen
