Normal Flora & Gastroenteritis

Normal Flora & Gastroenteritis

Metabolic:
 Fermentation of non-digestible dietary residue and gut mucus
 Salvage of energy as short-chain fatty acids
 Production of vitamin K

Trophic:
 Control of epithelial cell proliferation & differentiation
 Development & maintenance of the immune system

Protective:
 Protection against pathogens (barrier effect)

Causative Agents of Gastroenteritis:

 Viral – Rota virus, Noro virus, Adenovirus, Astro
 Bacterial – Campylobacter, E. coli, Shigella spp. Salmonella spp. Vibrio
cholerae, Yersinia enterocolitica etc.
 Parasitic – Entamoeba histolytica, Giardia lamblia Cryptosporidium
parvum

Mechanisms of Gastroenteritis:

 Toxins
o Enterotoxins eg V. cholerae, S. aureus (non-inflammatory)
o Cytotoxins eg Shigella, E.coli 0157, C. difficile (inflammatory)

 Attachment eg EPEC (non- inflammatory)

 Direct Invasion eg Salmonella, Shigella (penetrating)

 Impaired reabsorption eg Viruses, Parasites


Types of Escherichia. Coli that cause gastroenteritis:

 Enterotoxigenic (ETEC)
o Major cause of infant and traveller’s diarrhoea
 Enteropathogenic (EPEC)
o Diarrhoea in the tropics
o Little importance in industrialised countries
 Enterohaemorrhagic (EHEC)
o Zoonosis
o Haemolytic ureamic syndrome
 Enteroinvasive (EIEC)