Escherichia coli

Ah, E. coli, the bug everyone has heard of! A member of the family Enterobacteriaceae, E. coli is a Gram-negative, non-spore-forming rod, ~1-2 µm wide, 3-30 µm long:

The average human gut contains about 1 kg of bacteria. Of these, approximately 0.1% are normally E. coli. The presence of these bacteria within our intestines is necessary for normal development and health - E. coli, along with other types of enterobacteria, synthesize vitamins which are then absorbed by the body, e.g. vitamin K and B-complex vitamins. Although the normal habitat of this species is the gut, they can survive quite well outside the body in faecally-contaminated environments such as water or mud. Under these circumstances, they can be a useful indicator of sewage contamination ("faecal coliforms"). Phase contrast microscopy: E.coli is usually a motile organism, possessing peritrichous flagellae. However, the agar-grown cells in this video are not motile, simply moving due to Brownian motion:

When E. coli go bad ...

Different strains of E. coli are defined serologically by distinctive antigens:

• O antigens: derived from the cell wall
• H antigens: derived from flagella and only found on motile strains
• K antigens: derived from polysaccharide capsules secreted by the organism

Although most strains of E. coli are harmless and even beneficial, some isolates are capable of causing disease. Pathogenic "enterovirulent" E. coli strains are divided into groups based on pathogenic mechanisms:

• Enterohemorrhagic E. coli (EHEC) cause haemorrhagic colitis and haemolytic uraemia syndrome. E. coli O157:H7 is the principal stereotype in this group.
• Enteroinvasive E. coli (EIEC) cause a form of diarrhoea similar to Shigella infection.
• Enterotoxigenic E. coli (ETEC) are a major cause of traveller's diarrhoea and infant diarrhoea in developing countries. These strains product a heat-labile toxin and/or a heat-stable toxins.
• Enteropathogenic E. coli (EPEC) are an important cause of infant diarrhoea.
• Enteroadherent E. coli (EAEC) is the newest category to be added to the rogues gallery.

How to Prevent Food Poisoning: A Practical Guide to Safe Cooking, Eating, and Food Handling
by Elizabeth Scott, Paul Sockett.
Provides guidelines on how to prevent contamination in food prepared in the home, eat safely in restaurants, be sure the food you buy is safe, transport and store food, and properly prepare leftovers.
(Amazon.co.UK)

E.coli 0157: The True Story of a Mother's Battle With a Killer Microbe
by Mary Heersink.
E.coli 0157 was the bacterial culprit of the Jack-in-the-Box hamburger epidemic, during which it nearly took the life of young Damion Heersink. Damion's mother describes in detail the six-week roller-coaster assault of hemolytic uremic syndrome and thrombotic thrombocytopenic purpura that her son endured.
(Amazon.co.UK)