title: Transfer of trimethoprim resistance from fecal Escherichia coli isolated during a prophylaxis study in Mexico.
abstract: Forty-one of 100 trimethoprim-resistant fecal isolates of Escherichia coli isolated during a diarrhea prophylaxis study transferred trimethoprim resistance to an E. coli K12 derivative at frequencies ranging from 1 x 10(-7) to 2 x 10(-2). Analysis of these transconjugants, after attempting to select those that had received only one plasmid, revealed that 34 (83%) were resistant to trimethoprim plus only one or two of seven other antimicrobial agents tested, most often ampicillin and/or streptomycin. In contrast, 91% of the donor strains were resistant to four or more antimicrobial agents. Plasmid analysis demonstrated that a 35-megadalton plasmid was present in 35 transconjugants and was usually associated with resistance to trimethoprim, streptomycin, and ampicillin; 19 transconjugants had only a 35-megadalton plasmid and were resistant to only these three antimicrobial agents, raising the possibility that a common plasmid was present in many strains. Although resistance to multiple antimicrobial agents could be transferred to the K12 recipient, resistance to more than three agents was seldom mediated by a single plasmid. The high degree of transferability of trimethoprim resistance from these fecal isolates of E. coli emphasizes the potential for the dissemination of genes carrying trimethoprim resistance.
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003227:Conjugation, Genetic; D003967:Diarrhea / Q000517:prevention & control; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D005243:Feces / Q000382:microbiology*; D006801:Humans; D008800:Mexico; D011815:R Factors; D014295:Trimethoprim / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: D000900:Anti-Bacterial Agents; D014295:Trimethoprim