Beta-lactam resistance in aerobic faecal flora from general practice patients in the UK.

One hundred faecal specimens submitted to a diagnostic laboratory in Edinburgh and found to be negative for gastrointestinal pathogens were examined for the presence of antibiotic-resistant bacteria. The results were compared with findings in the healthy population in the same area. The highest incidence of resistance was observed to cefuroxime (65%) and ampicillin (60%). Of the ampicillin-resistant isolates, 62% could transfer their resistance determinants to a standard Escherichia coli host strain. In 100% of these transconjugants ampicillin resistance was shown to result from the presence of the TEM-1 beta-lactamase which was identified in a heterogeneity of plasmid profiles. These plasmids commonly mediated resistance to streptomycin and tetracycline in addition to ampicillin.