Author
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JARVIS, G - CORNELL UNIVERSITY |
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Russell, James |
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Submitted to: Journal of Molecular Microbiology and Biotechnology
Publication Type: Review Article Publication Acceptance Date: 9/27/2000 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Escherichia coli is a common gut bacterium, but it is usually out numbered by strictly anaerobic bacteria. When fecal material is exposed to oxygen, fermentation acids can be respired, and E. coli numbers increase. E. coli can survive for long periods of time in feces, but subsequent proliferation is dependent on its ability to re-enter gastrointestinal tract via contaminated water and food. The oral fecal lifestyle of E. coli is facilitated by its ability to survive the low pH of the human gastric stomach. Most strains of E. coli do not cause human disease, some strains produce toxins and other virulence factors. Mature cattle can carry E. coli O157:H7 without showing signs of infection, and beef can be contaminated with cattle feces at slaughter. Cattle manure is often used as a fertilizer by the vegetable industry, and E. coli from manure can migrate through the soil into water supplies. Sanitation, cooking and chlorination nhave been used to combat fecal E. coli, but these methods are not always effective. Recent work indicates that cattle diets can be modified to overcome the extreme acid resistance of E. coli. When cattle were fed hay for only a few days, colonic volatile fatty acid concentrations declined, pH increased, and the E. coli were no longer able to survive a pH shock that mimicked the human gastric stomach. E. coli in stored cattle manure eventually become highly acid resistant even if the cattle were fed hay, but these bacteria could be killed with a treatment that employed sodium carbonate. Because the diet manipulations and carbonate treatment affected E. coli in general rather than specific serotypes, there is an increased likelihood of successful field application. |
