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      Multiple-locus variable number of tandem repeat analysis (MLVA) of Irish verocytotoxigenic Escherichia coli O157 from feedlot cattle: uncovering strain dissemination routes

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          Abstract

          Background

          The identification of the routes of dissemination of Escherichia coli (E. coli) O157 through a cohort of cattle is a critical step to control this pathogen at farm level. The aim of this study was to identify potential routes of dissemination of E. coli O157 using Multiple-Locus Variable number of tandem repeat Analysis (MLVA).

          Results

          Thirty-eight environmental and sixteen cattle faecal isolates, which were detected in four adjacent pens over a four-month period were sub-typed. MLVA could separate these isolates into broadly defined clusters consisting of twelve MLVA types. Strain diversity was observed within pens, individual cattle and the environment.

          Conclusion

          Application of MLVA is a broadly useful and convenient tool when applied to uncover the dissemination of E. coli O157 in the environment and in supporting improved on-farm management of this important pathogen. These data identified diverse strain types based on amplification of VNTR markers in each case.

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          Most cited references23

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          Multilocus variable-number tandem repeat analysis distinguishes outbreak and sporadic Escherichia coli O157:H7 isolates.

          Escherichia coli O157:H7 is a major cause of food-borne illness in the United States. Outbreak detection involves traditional epidemiological methods and routine molecular subtyping by pulsed-field gel electrophoresis (PFGE). PFGE is labor-intensive, and the results are difficult to analyze and not easily transferable between laboratories. Multilocus variable-number tandem repeat (VNTR) analysis (MLVA) is a fast, portable method that analyzes multiple VNTR loci, which are areas of the bacterial genome that evolve quickly. Eighty isolates, including 21 isolates from five epidemiologically well-characterized outbreaks from Pennsylvania and Minnesota, were analyzed by PFGE and MLVA. Strains in PFGE clusters were defined as strains that differed by less than or equal to one band by using XbaI and the confirmatory enzyme SpeI. MLVA was performed by comparing the number of tandem repeats at seven loci. From 6 to 30 alleles were found at the seven loci, resulting in 64 MLVA types among the 80 isolates. MLVA correctly identified the isolates from all five outbreaks if only a single-locus variant was allowed. MLVA differentiated strains with unique PFGE types. Additionally, MLVA discriminated strains within PFGE-defined clusters that were not known to be part of an outbreak. In addition to being a simple and validated method for E. coli O157:H7 outbreak detection, MLVA appears to have a sensitivity equal to that of PFGE and a specificity superior to that of PFGE.
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            Contact with farming environment as a major risk factor for Shiga toxin (Vero cytotoxin)-producing Escherichia coli O157 infection in humans.

            In a prospective, unmatched case-control study of sporadic Shiga toxin (Vero cytotoxin)-producing Escherichia coli O157 (STEC O157) infection in England, exposure to the farming environment emerged strongly as a risk factor (adjusted odds ratio = 2.45; 95% confidence intervals = 1.49-4.02; p=0.0004) posing further challenges and opportunities for prevention.
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              Cattle water troughs as reservoirs of Escherichia coli O157.

              Environmental survival of Escherichia coli O157 may play an important role in the persistence and dissemination of this organism on farms. The survival of culturable and infectious E. coli O157 was studied using microcosms simulating cattle water troughs. Culturable E. coli O157 survived for at least 245 days in the microcosm sediments. Furthermore, E. coli O157 strains surviving more than 6 months in contaminated microcosms were infectious to a group of 10-week-old calves. Fecal excretion of E. coli O157 by these calves persisted for 87 days after challenge. Water trough sediments contaminated with feces from cattle excreting E. coli O157 may serve as a long-term reservoir of this organism on farms and a source of infection for cattle.
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                Author and article information

                Journal
                BMC Vet Res
                BMC Veterinary Research
                BioMed Central
                1746-6148
                2008
                24 January 2008
                : 4
                : 2
                Affiliations
                [1 ]Veterinary Food Safety Laboratory, Cork County Council, Inniscarra, Cork, Ireland
                [2 ]Centres for Food Safety & Food-borne Zoonomics, UCD Veterinary Sciences Centre, University College Dublin, Belfield, Dublin, Ireland
                [3 ]Food Safety Authority of Ireland, Abbey Court, Lower Abbey Street, Dublin 1, Ireland
                Article
                1746-6148-4-2
                10.1186/1746-6148-4-2
                2246123
                18218128
                2618b160-e0fd-43b3-988f-3ae14b0a40ef
                Copyright © 2008 Murphy et al; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 7 August 2007
                : 24 January 2008
                Categories
                Research Article

                Veterinary medicine
                Veterinary medicine

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