BETA-LACTAM RESISTANCE IN NORMAL FECAL FLORA FROM SOUTH-AFRICA

The genetic and biochemical basis of ampicillin resistance amongst the aerobic Gram-negative commensal faecal flora of healthy volunteers in South Africa has been determined. Amongst 608 ampicillin resistant st rains isolated from 320 of the participants, 158 were able to transfer their ampicillin resistant determinants into Escherichia coli K-12 J6 2-2. Iso-electric focusing of the beta-lactamases, extracted from the transconjugants, demonstrated that ampicillin resistance resulted from the presence of the TEM-1, TEM-2 and SHV-1 beta-lactamases in 94.3%: 2.5% and 32% of isolates respectively. Endonuclease restriction digest s of the plasmids isolated from the transconjugants showed that the be ta-lactamase genes were present on a wide variety of plasmid types; 10 1 distinct plasmid endonuclease restriction patterns were identified. Transferable ampicillin resistance was associated with resistance to o ther antibiotics at the following frequencies: trimethoprim (48.7%), s treptomycin (35.4%), tetracycline (27.2%), spectinomycin (9.5%), chlor amphenicol (32%) and gentamicin (1.3%). One antibiotic resistance patt ern: ampicillin and trimethoprim, predominated (28%). In total, 77.9% of the plasmids conferred resistance to other antibiotics raising the possibility that use of any of these agents, not simply ampicillin, ma y contribute to the maintenance of resistance genes.