Enterobacteriaceae Flashcards
Enterobacteriaceae
LARGE FAMILY of G Neg RODS !
Salmonella
Klebsiella
Shigella
Proteus
Enterobacters
Escherichia coli
Yersinia enterolitica
A large and diverse family of gram negative rods
Free living part of human and animal flora
By far the most common cause of UTIs
agents that spread diarrhea
can spread to bloodstream and cause endotoxic shock
Bacteriology of Enterobacteriaceae
1. classifications
2. Components of their cell wall ?
3. what are the three major surface antigens of enterobacteriacae?
4. All Enterobacteriaceae: Glucose, reduction of nitrates and oxidase processes
1.coccobacilli and filamented rods
NO SPORES
NO acid-fast
2. LPS is called the O antigen “ repeated oligosaccharide linked to Lipid A
3. O , H and K antigens
4. ALL ENTEROBACTERIACEAE:
*** Reduce nitrates to nitrites,
* ferment glucose and are
* OXIDASE NEGATIVE **
O: polysaccharides attached to LIPID A outermemberane
K: polysaccharide capsule; slime layer
H: flagellar protein
common Antigenic proteins of enterobacteriaceae
surface pili
Growth and Incubation
Both
Aerobic
Anaerobic
produces 2 -5 mm colonies on AGAR media
12 -18 hour incubation
Fermentation:
which Enterobacteriaceae ferment glucose ?
All of them
Toxins involved with Enterobacteriaceae
All have** LPS** “some” have **exotoxins **
Cytotoxins kill cells
Enterotoxins cause secretion and diarrhea
Remeber protein exotoxins: INHIBIT protein cell synthesis
Action of enterotoxin
act on intestinal enterocytes, causing the net secretion of water and electrolytes to produce diarrhea.
Enterotoxin is strongly associated with E.coli, Shigella, Yersinia and other species
where are colonies situated by nature
“normal environment”
female genital tract
lower GI
skin
respiratory tracts
They can live here normally
Enterobacteriaceae members found living in normal flora
- E.coli (most common)
- Klebsiella
- Proteus
- EnterBACTER spiecies
Note: Salmonella and Shigella are NOT members of the normal flora, although carrier states can exist.
Enterobacteriaceae organism that are only classified as **human pathogens **
NO animal reservoirs
Salmonella Typhi and Shigella
Explain the pathogenesis of Enterobacteriaceae:
These guys are poised to “take advantage” of their “common” presence in the normal environmental flora TO produce disease when they gain access to other body sites where they do NOT belong !
okay so if they are living in the female genital tract as normal, that means if these bacteria access some where else in the body then it will cause disease.
Prototype of oppurtunistic infection “crossing barriers” moving to places where they dont belong is:
give an example of the most common prototype of the disease ?
UTI
Colonization presents oppurtunity when defense barriers are open
follows adherence and access to the bladder
Intestinal Infections:
Give three members of the enterobacteriaceae family
- Salmonella
- Shigella
- Yersinia enterolitica
note; Also strains of E. coli can produce in the intestinal tracts
Name virulence factors of
Salmonella, Shigella and Yersinia that correlates with the diarrhea they produce ?
Enterotoxin
Cytotoxin
Differentiate the main virulence factor
Cytotoxin and enterotoxin in terms of type of diarrhea produced:
Invasive and cytotoxic strains produce “Dysentry” “inflammatory diarrhea” composed of WBC and/or blood
Enterotoxin-producing strains: cause “watery diarrhea”
Primry feature: fluid loss (dehydration)
The gut is the portal entry for these diseases but it is considered systemic as the gut delivers everything to the blood ! Bacteria can sprread in multiple organs
