Author
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Shelton, Daniel |
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 11/24/2010 Publication Date: 12/9/2010 Citation: Shelton, D.R. 2010. Enterohemorrhagic E. coli (EHEC): “stealth” agents adept at avoiding detection.[abstract]. Interpretive Summary: Technical Abstract: Enterohemorrhagic E. coli (EHEC), which are typically associated with water- or food-borne outbreaks, are not considered to be “select agents”, presumably because they have low morality rates and are already present in water and raw foods. However, as “stealth” bioterrorism agents, designed to destroy confidence in water and food supplies, they have many desirable attributes. E. coli O157:H7 was the first EHEC to be described. Because of unique physiological traits, it is readily isolated from environmental and stool samples. However, many other strains of EHEC have now been described which are not easily distinguished from generic E. coli making rapid identification/isolation problematic. The most virulent EHEC strains carry a suite of virulence genes (e.g., stx, eae, hly) that are widely distributed among E. coli and other enteric bacteria. For example, stx genes (encoding for shiga toxins) are carried on lysogenic phages that can be transmitted among a variety of enteric bacteria; the eae gene is located on a “pathogenicity island” (LEE) that is widely distributed among E. coli; while the hly genes (encoding for hemolysin) are located on a plasmid that can be mobilized among different enteric bacteria. These genes are ubiquitous in water-borne enteric populations and are frequently present simultaneously in independent strains. Consequently, the high rate of false positives makes even presumptive detection in environmental samples virtually impossible. Finally, EHEC strains can be easily cultured using primitive facilities and since antibiotic treatment for EHEC infections is not recommended, no manipulation is required to select for antibiotic resistant strains. |
