fulltext.study @t Gmail

Occurrence of virulence genes associated with enterohemorrhagic Escherichia coli in raw municipal sewage

Paper ID Volume ID Publish Year Pages File Format Full-Text
4773 244 2007 7 PDF Available
Title
Occurrence of virulence genes associated with enterohemorrhagic Escherichia coli in raw municipal sewage
Abstract

Municipal sewage influent was screened for the presence of the virulence genes encoding Shiga-like toxins SLT-I and SLT-II (slt-I and slt-II) and intimin (eaeA) and those involved in biosynthesis of O157 (rfbE) and H7 (fliC) antigens by multiplex PCR to simultaneously identify the enterohemorrhagic Escherichia coli (EHEC) O157:H7 and its virulence factors in a single reaction. The screening was carried out monthly from October 2004 to September 2005. Direct PCR analysis using total DNA from sewage concentrate showed the presence of at least one virulence gene in 100% samples (n = 12). Sixty six percent of these samples were also positive for rfbE (O157) gene and fliC (H7) gene. The PCR amplification of these genes was possible when the concentration was above 20 cells ml−1. From the multiplex PCR of the isolates following plating on Cefixime-Tellurite Sorbitol MacConkey (CT-SMAC) agar to detect non-sorbitol fermenting (NSF) colonies (n = 600), one E. coli strain carrying slt-II gene and two strains of E. coli O157:H7 carrying slt-I were detected. The results show that municipal sewage represents a potential reservoir of EHEC. CT-SMAC agar was proved to have limited E. coli O157:H7 selectivity and only 0.005% (3/600) sensitivity for sewage samples due to the high frequency (43%) of NSF strains in sewage. The enrichment of sewage sample in modified E. coli broth (mEC) increased the sensitivity of PCR resulting in the clearer amplification of five genes. Amplification of target cell type in mEC broth implied that EHEC were present in sewage in a culturable and hence potentially infectious state. However, pre-enrichment did not affect the selectivity of CT-SMAC because frequency of NSF colonies remained the same as that obtained without enrichment. The study, therefore, underscores the need for more sensitive screening techniques that can be routinely employed for the regular monitoring of sewage influent.

Keywords
Enterohemorrhagic E. coli (EHEC); E. coli O157:H7; Municipal sewage; Sorbitol MacConkey agar; Modified E. coli broth
First Page Preview
Occurrence of virulence genes associated with enterohemorrhagic Escherichia coli in raw municipal sewage
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us
Publisher
Database: Elsevier - ScienceDirect
Journal: Biochemical Engineering Journal - Volume 33, Issue 1, January 2007, Pages 53–59
Authors
, , , ,
Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us