Escherichia coli 0157:H7 Essay -- Essays Papers

Escherichia coli 0157:H7 Encounter and history: Escherichia coli are gram negative, rod shaped bacteria that are often used in laboratory studies and are usually harmless, residing in the human digestive tract as part of the normal flora. E. coli 0157:H7 is a pathogenic strain of E. coli that was first identified as a cause of disease in the United States in 1982, during an investigation into an outbreak of gastrointestinal illness. The organism is also called enterohemorrhagic E. coli (EHEC) because it causes abdominal pain with diarrhea that may contain blood. It lives in the intestines of healthy cattle and can contaminate meat during slaughter. It is believed that the widespread use of antibiotics by American farmers has promoted the horizontal gene transfer of antibiotic resistance genes and pathogenicity islands that has led to the creation of new pathogenic strains such as E. coli 0157:H7. The verotoxins that cause the disease are also called shiga toxins because they were acquired from Shigella strains. The illness predomi nantly occurs in the U.S., Canada, Japan and other industrialized nations of Europe. The average incidence in most countries ranges from 1-30 per 100,000 and the number of confirmed cases is increasing. In the U.S, about 73,000 people are infected anually, with an average of 61 deaths per year. Entry, Spread and Multiplication: After food contaminated with E. coli 0157:H7 is ingested, it travels through the digestive system and attaches to the mucosal epithelial cells of the large intestine and forms a pedestal, which leads to destruction of the microvili. The bacteria will then multipy and produce toxins, which, in addition to diarrhea cause vomiting in 50% of cases and fever in 30%. The av... ...ays to prevent contamination of EHEC during the growth, slaughter, proccesing of beef. A vaccine for cattle is not practical because the bacteria do not cause illness in cattle and therefore do not stimulate their immune response. It is recommended that physicians have any patient with bloody diarrhea tested for EHEC. There are a variety of ways to detect it in the laboratory. It is possible to screen for EHEC by inoculating stool specimens onto MacConkey medium containing sorbitol instead of lactose. PCR tests for verotoxin are also available. References: http://www.who.int/inf-fs/en/fact125.html http://www.cdc.gov/ncidod/dbmd/diseaseinfo/escherichiacoli_g.htm http://www.cps.ca/english/statements/ID/id95-03.htm http://www.enceph.com/feature_archive/gastro/v25n4p205.html http://microbes.historique.net/ecoli.html http://www.i-sis.org.uk/ecoli.php