title: Trimethoprim resistance in South African isolates of aerobic gram-negative faecal flora.
abstract: Aerobic gram-negative commensal faecal flora from 362 healthy volunteers was examined for resistance to trimethoprim. Three hundred fifty-seven trimethoprim-resistant organisms were isolated from 272 of the volunteers (297 Escherichia coli, 46 Klebsiella spp., 9 Enterobacter spp. and 7 other species). Trimethoprim resistance was associated with resistance to other antibiotics at the following frequencies: ampicillin 71.4%, tetracycline 88%, cephalosporins 14% and aminoglycosides 4%. High-level resistance to trimethoprim (MIC > or = 1024 mg/l) occurred in 98.6% of the isolates. Trimethoprim resistance was transferable in 51.2% of the isolates. An X+ factor was required to mobilize resistance in a further 3.4%. Resistance to other antibiotics cotransferred with trimethoprim at the following frequencies: ampicillin 55.4%, tetracycline 30%, cephalosporins 1.5% and aminoglycosides 2.6%. Restriction enzyme analysis of 148 plasmids revealed 79 different profiles. Two restriction profiles represented 10.1 and 8.8% of these plasmids, respectively. The large number of different antibiograms and restriction profiles indicates that there is a large gene pool of trimethoprim-resistant organisms in the faecal flora.
authors.affiliation: Department of Medical Microbiology, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: P V
authors.initials: PV
authors.lastname: Adrian
authors.forename: H J
authors.initials: HJ
authors.lastname: Koornhof
authors.forename: B A
authors.initials: BA
authors.lastname: Wylie
mesh_terms: D001420:Bacteria, Aerobic / Q000187:drug effects*; D003227:Conjugation, Genetic; D004352:Drug Resistance, Microbial; D005243:Feces / Q000382:microbiology*; D006090:Gram-Negative Bacteria / Q000187:drug effects*; D006801:Humans; D008826:Microbial Sensitivity Tests; D010957:Plasmids; D014295:Trimethoprim / Q000494:pharmacology*
chemical_list: D014295:Trimethoprim