Low minimum inhibitory concentrations associated with the tetracycline-resistance gene tet(C) in Escherichia coli.

Twenty-eight Escherichia coli isolates from various animal and environmental sources with defined tetracycline-resistance genotypes for tet(A), tet(B), and tet(C) were tested for their susceptibility to tetracycline by means of both broth microdilution and Etest. All tet(C)-positive isolates had tetracycline minimum inhibitory concentrations clustering around an intermediate susceptibility range of 2 to 16 microg/mL. Detecting tet(C)-positive isolates by means of susceptibility testing may therefore be difficult with use of the current breakpoint for tetracycline of the Clinical and Laboratory Standards Institute guidelines.

Distribution of sulfonamide resistance genes in Escherichia coli and Salmonella isolates from swine and chickens at abattoirs in Ontario and Québec, Canada.

Sulfonamide-resistant Escherichia coli and Salmonella isolates from pigs and chickens in Ontario and Québec were screened for sul1, sul2, and sul3 by PCR. Each sul gene was distributed differently across populations, with a significant difference between distribution in commensal E. coli and Salmonella isolates and sul3 restricted mainly to porcine E.

Antimicrobial resistance in Escherichia coli isolates from swine and wild small mammals in the proximity of swine farms and in natural environments in Ontario, Canada.

Wild animals not normally exposed to antimicrobial agents can acquire antimicrobial agent-resistant bacteria through contact with humans and domestic animals and through the environment. In this study we assessed the frequency of antimicrobial resistance in generic Escherichia coli isolates from wild small mammals (mice, voles, and shrews) and the effect of their habitat (farm or natural area) on antimicrobial resistance. Additionally, we compared the types and frequency of antimicrobial resistance in E.

Effect of plasmid pTENT2 on severity of porcine post-weaning diarrhoea induced by an O149 enterotoxigenic Escherichia coli.

A particularly virulent O149:H10 enterotoxigenic Escherichia coli clone harbours a newly characterized plasmid pTENT2 carrying the tetracycline-resistance tetA and the virulence genes estA, paa, and sepA that were not present in less virulent clones. The objectives of this study were to assess whether the additional genes on pTENT2 played a role in the increased severity of post-weaning diarrhoea and if they provided any potential advantage for the emergence of the highly virulent clone. Groups of pigs were dosed orally with isogenic pTENT2-positive and pTENT2-negative ETEC strains, and the clinical and pathological changes were compared between the groups.