Gram-Negative Rods: Enterobacteriaceae Flashcards
Proteobacteria are _______ or ______
Gram negative rods; cocci
Enterobacteriaceae
Gram neg rods, free living (saphrophytes)
- part of indigenous flora of people and animals
- metabolically active
- fast growing under aerobic and anaerobic conditions
- motile
- acid-fast (spore forming)
- opportunistic pathogens
Enterobacteriaceae are primarily inhabitants of the ________
Lower GIT
- main facultative anaerobic portion of bacterial content of the cecum and colon
Other locations of enterobacteriaceae
- female genital tract
- transient colonizers of skin and oral cavity
- respiratory tract (small numbers) –> increase in hospitalized patients
What is the most common species among the indigenous flora of mammals and some birds?
E. coli
- followed by: Klebsiella, proteus, and enterobacter
What species are primarily pathogenic and not part of the normal flora?
- salmonella
- shigella
- certain strains of E. coli
- yersinia
Length may vary from ____ to ________
Large coccobacilli; elongated, filamentous rods
Sides are _____, ends are _____
Parallel; round
Morphological features
- motile strains have peritrichous flagella
- fimbriae
- capsules and/or slime layers
- typical features of GN bacteria (cell wall, cell membrane, etc)
Growth
Readily grow on simple media (facultative anaerobes)
- resistance to bile salts and many bacteriostatic dyes
- grow under almost any conditions –> interferes with isolation of fastidious bacteria when looking at clinical specimens
What 3 morphological features are used for identifying and subtyping?
- LPS
- capsule/slime layer
- flagellar antigens
H, K, and O antigens
H antigens: flagella (protein)
K antigens: capsule/slime layer (polysaccharides)
O antigens: LPS (polysaccharide)
What do all enterobacteriaceae have in common?
All are:
- facultative anaerobes
- ferment glucose (with gas produced)
- reduce nitrates to nitritie
- cytochrome oxidase negative!!
Rapid fermentation of lactose is a useful characteristic for ________
Initial differentiation
- most common members of intestinal flora ferment lactose promptly in more than 90% of isolates
- most (esp intestinal pathogens) are rarely positive
What are common toxins produced by all enterobacteriaceae?
All possess:
- LPS (endotoxin)
- –> leads to: fever, leukopenia, activation of blood coag factors)
- some produce exotoxins
Most enterobacteriaceae only infect a host under _______
Predisposing circumstances
- stress, lack of colostrum, change in diet, infections, antibiotics, etc
Members of normal flora act as opportunistic pathogens when ______
They are displaced from their normal site or if local/systemic defense mechanisms are damaged
What are the most common sites of opportunistic infections?
Wound and urogenital tract infections
- may occur at any body site, especially in septicemia
What contributes to the antimicrobial susceptibility of enterobacteriaceae?
Combo of chromosomal and plasmid-mediated resistance make them the most variable
What antibiotics are these bacteria usually resistant to?
- penicillin G (except in the urinary tract)
- erythromycin
- clindamycin
What is the major facultative anaerobic species of bacteria in the intestine of warm-blooded animals throughout their life?
E. coli
Aerobic culture of feces or intestinal contents yields ____
E. coli
What are the major diseases caused by E. coli?
- enteric infections
- septicemia
- urinary tract infections
- mastitis
How do you identify E. coli?
- biotyping
- serotyping
- phage-typing
- colicin-typing
- virulence factor expression
