E. Coli Primer -- O157:H7 and others

Via 3 Quarks learn more than you wanted to know about contaminated spinach. Here is a short course in microbiology.

There's a fascinating--albeit gruesome--backstory to this outbreak, which I've been researching for my next book, a portrait of Escherichia coli. Escherichia coli is regular inhabitant of the human gut... You carry about a trillion harmless E. coli. E. coli has also become the model par excellence for understanding the nuts and bolts of life. Lots of Nobel Prizes were awarded for research on these fascinating bugs.

Over the twentieth century, scientists began to discover that some strains of Escherichia coli are not so nice. A group of strains called Shigella cause diarrhea, for example, killing over a million people a year. And new virulent strains keep turning up. In March 1982, 25 people in Medford, Oregon, developed cramps and bloody diarrhea. The doctors identified a strain of Escherichia coli in some of the patients. The strain could not be found among the records of the Centers for Disease Control. That had never happened before. Three months later, another outbreak occurred in Traverse City, Michigan. The source of the bacteria proved to be undercooked hamburgers that the victims had eaten at a McDonald's restaurant. Scientists named the strain O157:H7--a code for its distinctive surface molecules--and began to hunt for it among the bacteria that had been isolated from patients in earlier years. Out of 3,000 strains collected from American patients, a single one proved to be O157:H7, isolated from a woman in California in 1975. Searches in Great Britain and Canada turned up seven more cases, none before 1975.

...About 28% of cows in the United States are estimated to carry O157:H7. It can get into people through contaminated meat thanks to bad butchering (a single crumb of undercooked meat carrying 100 bacteria is enough for a potentially fatal infection). The animals also release the bacteria in their manure, from which it can be spread to vegetables and fruits, perhaps by the wind, slugs, or flies. It is also the reason why you really must wash your hands if you visit a petting zoo.

It gets worse.
Finish reading (and whatever else you need to do) at the link.