AEM Accepts, published online ahead of print on 13 June 2008

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Appl. Environ. Microbiol. doi:10.1128/AEM.00517-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Transfer of Class 1 Integron Mediated Antibiotic Resistance Genes from Shiga Toxin Producing Escherichia coli to a Susceptible E. coli K-12 Strain in Storm Water and Bovine Feces

SUPAKANA NAGACHINTA and JINRU CHEN^*

The Department of Food Science and Technology, The University of Georgia, 1109 Experiment St. Griffin GA 30223-1797

^* To whom correspondence should be addressed. Email: jchen{at}uga.edu.

Transfer of class 1 integron mediated antibiotic resistance genes has been demonstrated under laboratory conditions. However, knowledge on the transfer of the genes in an agricultural environment is lacking. The present study sought to determine if integron mediated streptomycin and sulfisoxazole resistance genes could be transferred from Shiga toxin producing Escherichia coli (STEC) 6-20 (O157:H7) and 7-63 (O111:H8) to a susceptible strain of E. coli K12 MG1655 in bovine feces (pH 5.5, 6.0 or 6.5) and storm water (pH 5, 6, 7 or 8) at 4, 15, or 28°C, which are average seasonal temperatures for winter, spring-fall, and summer, respectively in Griffin, GA area. The results indicated that at 28°C, the integron mediated antibiotic resistance genes were transferred from both the STEC donors in bovine feces. Higher conjugation efficiencies were however, observed in the conjugation experiments involving STEC 6-20. In storm water, the resistance genes were only transferred from STEC 6-20. Greater numbers of transconjugants were recovered in the conjugation experiments in bovine feces with a pH value of 6.5, and in storm water with a pH value of 7. Antibiotic susceptibility tests confirmed the transfer of integron mediated streptomycin and sulfisoxazole resistances as well as the transfer of non-integron mediated oxytetracycline and tetracycline resistances in the transconjugant cells. These results suggest that the antibiotic resistance genes in STEC could serve as a source of antibiotic resistance genes disseminated via conjugation to susceptible cells of other E. coli strains in an agricultural environment.