Enterobacteriaceae PART1 Flashcards
Sites where members of the enterobaacteriaceae are considered “usual flora”
GI tract, uncommon normal flora of other areas
Sites where members of the enterobacteriaceae are considered always pathogenic
Normally sterile areas
Characteristics that are common among all members of Enterobacteriaceae
- GNR - straight
- Facultative anaerobes
- Peritrichous flagella (if motile)
- Ferment glucose
- Nitrates reduced to nitrites
- Oxidase negative
- Grow well on Mac agar
What Enterobacteriaceae generally look like on a SBA
Large, smooth, grey colonies on SBA
Factors which contribute to pathogenicity of Enterobacteriaceae (8)
- Endotoxins
- Exotoxins
- Invasiveness
- Adherence to epithelial cells
- Capsules
- Colonization
- Certain antigens
- Hemolysins/ Enzymes
When trying to isolate from areas with normal flora you may need to….?
Add several types of differential and selective media
- stool- MAC, HECK, XLD for example
5 identification schemes of identifying Enterobacteriaceae
- Crosshatch/checkerboard
- Grouping systems
- Branching Flow Diagrams
- Numerical coding systems
Problem with crosshatch/ checkerboard methods
Accurate but tedious
Problem with Grouping Systems (Edwards and Ewing)
Quicker but additional material may be needed
Problem with Branching Flow Diagrams
Simple but dangerous
-atypical organisms may be misidentified
Problem with coding systems
Need to use your brain not rely strictly on the number identification
Purpose of serologic typing
- identification of isolate
- Epidemiologic “fingerprinting” (helps trace where its coming from)
Most frequently serotyped GNRs
Salmonella
Shigella
Escherichia coli (selective isolates)
Serologic Typing Antigenic Structure
- K (name and 3 facts)
Capsular antigen
- polysaccharide
- heat labile
- may block O antigen
Serologic Typing Antigenic Structure
- H (name and two facts)
Flagellar antigen
- protein
- heat labile
