Original URL: http://www.theregister.co.uk/2006/09/08/the_odd_body_ecoli/

Why don't we suffer from E. coli all the time?

Beneficial bacteria?

By Stephen Juan

Posted in Science, 8th September 2006 15:32 GMT

Also in this week's column:

Why don't we suffer from E. coli all the time? How soon does E.coli colonise in the intestines of a newborn baby, and how does it get into the intestines?

Asked by Neil Greenwood of Cardiff, Wales

All bacteria in the gut comes from the environment and is ingested during feeding. While the mother's milk should be sterile, other environmental factors allow bacteria to enter. Bacteria colonises the mouth first. It is swallowed in large numbers along with the milk.

E. coli (Escherichai coli) is one of a diverse group of microorganisms called coliforms. Coliforms are classified mostly by the tests for their isolation rather than for any physical characteristics. They are found in the lower gastrointestinal tract of humans and animals. Coliforms are unlikely to grow in water, but they grow nicely in food especially if the food is kept at conditions that may enhance growth. Room temperature on a warm day is certainly enough!

E. coli ferments and lives on the lactose of milk. Fermentation is an enzymatically controlled anaerobic breakdown or transformation of an energy-rich organic compound. Carbohydrate to carbon dioxide and alcohol to an organic acid are examples of fermentation.

E. coli colonises almost immediately. Most forms of E. coli are not capable of causing disease (non-pathogentic). They are found in large numbers in the gut.

They can be beneficial to humans in that they keep dangerous bacteria at bay and produce various vitamins that the body absorbs from the colon. However, some strains can cause disease (pathogenic). E. coli 0157 and E. coli 0111 are examples of these. E. coli has been implicated in some severe food poisonings in every corner of the world.

Stephen Juan, Ph.D. is an anthropologist at the University of Sydney. Email your Odd Body questions to s.juan@edfac.usyd.edu.au