Exam 3: Gram-negative Rods Part 1: Enterobacteriaceae Flashcards
What are the different types of proteobacteria?
Alphaproteobacteria
Betaproteobacteria
Gammaproteobacteria
What is enterobacteriaceae?
A large and diverse family of gram negative rods found free living and as part of the indigenous flora of people and animals
How do enterobacteriaceae grow?
Rapidly under aerobic and anaerobic conditions and are metabolically active
What is enterobacteriaceae a primary inhabitant of?
Lower GI tract
It is the main facultative anaerobic portion of the bacterial content of the cecum and colon
What are other places that enterobacteriaceae can be found?
Female genital tract
Transient colonizers of the skin and oral cavity
Small numbers may be present in the respiratory tract of healthy animals
What is the most common species of enterobacteriaceae among the indigenous flora of mammals and some birds?
E. coli
What is the morphology of enterobacteriaceae?
Medium-sized gram negative rods
What is used for the identification and subtyping of enterobacteriaceae?
LPS, capsule/slime layer, and flagellar antigens
What is flagella called as antigenic determinants?
H antigens
What are cell surface polysaccharide (capsule, slime layer) antigens called?
K antigens
What does LPS contain?
O polysaccharide chains called O antigens
What are features of enterobacteriaceae that contribute to classification?
All are facultative anaerobes
All ferment glucose
All reduce nitrates to nitrite
All are cytochrome oxidase negative
What is a useful characteristic for initial differentiation of enterobacteriaceae?
Rapid fermentation of lactose
What are the toxins of enterobacteriaceae?
All possess LPS and its effects are often seen in infections
Some produce exotoxins
Describe the pathogenicity of enterobacteriaceae
Some species have unique pathogenic features that allow them to produce GI or systemic infections in previously healthy animals
Most do no infect unless predisposing infections occur
What are the most common sites of opportunistic infections with enterobacteriaceae?
Wound and urogenital tract infections, but they may occur at any body site, especially in septicemia
What makes enterobacteriaceae the most variable of all bacteria in susceptibility to antimicrobial agents?
Combination of chromosomal and plasmid-mediated resistance
What is enterobacteriaceae usually resistant to?
High concentration of penicillin G, erythromycin, and clindamycin
What is E. coli the dominant species of in aerobic culture?
Feces or intestinal yields
What are the major diseases caused by E. coli?
Enteric infections
Septicemia
Urinary tract infections
Mastitis
What are the various schemes that E. coli can be identified by?
Biotyping Serotyping Phage-typing Colicin-typing Virulence factor expression
How many O, K, and H antigens have been identified with E. coli with serotyping?
174 O antigens
80 K antigens
53 H antigens
What are the 6 classes of E. coli that cause diarrheal disease?
Enterotoxigenic E. coli (ETEC) Enteroinvasive E. coli (EIEC) Enterohemorrhagic E. coli (EHEC) Enteropathogenic E. coli (EPEC) Enteroaggregative E. coli (EAEC) Adherent-invasive E. coli (AIEC)
What is ETEC an important cause of?
Diarrhea in infants and travelers in regions of poor sanitation
