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Applied and Environmental Microbiology, September 2008, p. 5414-5421, Vol. 74, No. 17
0099-2240/08/$08.00+0     doi:10.1128/AEM.00854-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Prevalence and Genetic Characterization of Shiga Toxin-Producing Escherichia coli Isolates from Slaughtered Animals in Bangladesh

Mohammad A. Islam,^1,2,3* Abdus S. Mondol,¹ Enne de Boer,² Rijkelt R. Beumer,³ Marcel H. Zwietering,³ Kaisar A. Talukder,¹ and Annet E. Heuvelink²

Enteric and Food Microbiology Laboratory, International Centre for Diarrhoeal Disease Research, Bangladesh, GPO Box 128, Dhaka-1000, Bangladesh,¹ Food and Consumer Product Safety Authority, P.O. Box 202, 7200 AE Zutphen, The Netherlands,² Laboratory of Food Microbiology, Wageningen University, 6700 EV Wageningen, The Netherlands³

Received 15 April 2008/ Accepted 7 July 2008

To determine the prevalence of Shiga toxin (Stx)-producing Escherichia coli (STEC) in slaughter animals in Dhaka, Bangladesh, we collected rectal contents immediately after animals were slaughtered. Of the samples collected from buffalo (n = 174), cows (n = 139), and goats (n = 110), 82.2%, 72.7%, and 11.8% tested positive for stx₁ and/or stx₂, respectively. STEC could be isolated from 37.9%, 20.1%, and 10.0% of the buffalo, cows, and goats, respectively. STEC O157 samples were isolated from 14.4% of the buffalo, 7.2% of the cows, and 9.1% of the goats. More than 93% (n = 42) of the STEC O157 isolates were positive for the stx₂, eae, katP, etpD, and enterohemorrhagic E. coli hly (hly_EHEC) virulence genes. STEC O157 isolates were characterized by seven recognized phage types, of which types 14 (24.4%) and 31 (24.4%) were predominant. Subtyping of the 45 STEC O157 isolates by pulsed-field gel electrophoresis showed 37 distinct restriction patterns, suggesting a heterogeneous clonal diversity. In addition to STEC O157, 71 STEC non-O157 strains were isolated from 60 stx-positive samples from 23.6% of the buffalo, 12.9% of the cows, and 0.9% of the goats. The STEC non-O157 isolates belonged to 36 different O groups and 52 O:H serotypes. Unlike STEC O157, most of the STEC non-O157 isolates (78.9%) were positive for stx₁. Only 7.0% (n = 5) of the isolates were positive for hly_EHEC, and none was positive for eae, katP, and etpD. None of the isolates was positive for the iha, toxB, and efa1 putative adhesion genes. However, 35.2% (n = 25), 11.3% (n = 8), 12.7% (n = 9), and 12.7% (n = 9) of the isolates were positive for the lpf_O113, saa, lpfA_O157/01-141, and lpfA_O157/OI-154 genes, respectively. The results of this study provide the first evidence that slaughtered animals like buffalo, cows, and goats in Bangladesh are reservoirs for STEC, including the potentially virulent STEC strain O157.

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* Corresponding author. Mailing address: Enteric and Food Microbiology Laboratory, Laboratory Sciences Division, ICDDR,B, GPO Box-128, Dhaka-1000, Bangladesh. Phone: 880 2 8860523. Fax: 880 2 8812529 or 880 2 8823116. E-mail: maislam{at}icddrb.org

Published ahead of print on 18 July 2008.

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Applied and Environmental Microbiology, September 2008, p. 5414-5421, Vol. 74, No. 17
0099-2240/08/$08.00+0     doi:10.1128/AEM.00854-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.