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- Gram Negative Enteric Bacteria
- Large heterogeneous group
- Gram negative rods
- Not Spore-forming
- Facultative aerobes or anaerobes
- Natural habitat is GIT
Endotoxins
- Complex lipopolysaccharides derived from bacterial cell walls
- Often released when bacteria lyse
Effects
- Similar regardless of bacterial origin
- Fever
- Act on various cells
- Especially Neutrophils
- Cause release of endogenous pyrogens
- Acute phase reactants
- Hypotension
- Early vasoconstriction (Chill)
- Later vasodilatation & ↑ vascular permeability
- Leads to Shock & Metabolic acidosis
- Inflammatory Response
- Activation of Complement Cascade
- With release of vasoactive substances
- Activation of coagulation cascade with DIC
Death
- Due to
- DIC & Exotoxins
- Organ failure secondary to shock
Exotoxins
- Most common are Enterotoxins
- Produce diarrhoea
- Produced by
- E coli (Traveller’s diarrhoea)
- Shigella (Dysentery)
- Vibrio Cholerae (Cholera)
Groups
Coliforms
- Aerobic rods found in GIT
- Large & heterogeneous group
- All resemble prototype Escherichia coli
- Other groups are
- Klebsiella
- Enterobacter
- Serratia
- Constitute large part of normal aerobic intestinal flora
- Become pathogenic when reach tissues outside intestine
- Commonest cause of UTI
- Various sensitivities
- Most sensitive to Gentamicin
Pseudomonas
- Motile aerobic Gram negative Rods
- Widely distributed
- May be found in intestine & skin
- Only pathogenic in areas with no defence
- Forms blue-green pus & sweetish odour
- Common infection in respiratory tract
- Treatment with
- Ceftazidime (3rd generation cephalosporin)
- Ticarcillin (anti-pseudomonal penicillin)
- Ciprofloxacin (quinolone)
Proteus
- Motile aerobic rods found in water
- Cause Chronic UTI
- Treatment with
Others
- Enterobacteriaceae
- Salmonellae
- Shigella
- Vibrio
- Campylobacter
