title: Conjugative transmission of antibiotic-resistance from stream waterEscherichia colias related to number of sulfamethoxazole but not class 1 and 2 integrase genes.
abstract: A conjugation assay was used to determine the effects of phenotypic resistance to one to up to 5 antibiotics, sampling site of origin, presence or absence of class 1 and/or class 2 integrase (intI) genes (intI1andintI2), and the number of sulfamethoxazole resistance (sul) and trimethoprim resistance (dfr) genes on the transfer frequencies of plasmids from environmental, antibiotic-resistantEscherichia coli. Of 51 sulfamethoxazole and trimethoprim-resistantE. coliisolates conferring at least onemobgene (mobP51, mobF11, mobF12, mobQ11, mobQ12, ormobQu), 38 produced transconjugants with an overall mean frequency of 1.60 × 10-3transconjugants/ donors (T/D) or 5.89 × 10-3transconjugants/recipients (T/R). The presence or absence ofintI1andintI2and the presence or absence of different targeteddfrgenes (dfrA1, dfrA8, dfrA12, dfrA14, dfrA17, and/ordfrB3) were not statistically related to plasmid transfer frequencies as determined by ANOVA (P≥ 0.05). However,E. coliisolates recovered 2 km downstream of wastewater treatment plant effluent input, and those possessing resistance to 3 antibiotics had significantly greater plasmid transfer frequency than their counterparts when calculated as T/D (ANOVA followed by Fisher's least significant difference means comparison,P< 0.05). Greater plasmid transfer frequency calculated as T/D was also measured forE. colipossessing 3 compared to a singlesulgene. The in-vitro frequency suggests that horizontal gene transfer of conjugative mediated-antibiotic (sul) resistance genes may be significant among resistant, stream bacteria.
authors.affiliation: Cell and Molecular Biology, Department of Crop, Soil, and Environmental Sciences, University of Arkansas, Fayetteville, AR, USA; Department of Biology, Faculty of Sciences, Syiah Kuala University, Banda Aceh, Indonesia.
authors.forename: Suhartono
authors.initials: S
authors.lastname: Suhartono
authors.affiliation: Cell and Molecular Biology, Department of Crop, Soil, and Environmental Sciences, University of Arkansas , Fayetteville, AR, USA.
authors.forename: Mary
authors.initials: M
authors.lastname: Savin
keywords: antibiotic resistance; conjugation; horizontal gene transfer; integron; mobilization