Molecular epidemiology of the plasmid-encoded TEM-1 beta-lactamase in Scotland

A survey of the beta-lactamases responsible for ampicillin resistance in urinary Escherichia coli isolated in central Scotland has been performed. The TEM-1 beta-lactamase was found to be most prevalent occurring in 88.2% of ampicillin-resistant isolates tested. Forty-six percent of the TEM-1 producing strains were able to transfer this resistance to E. coli J62-2 at 37 degrees C. Analysis of the resulting transconjugants revealed that the degree of resistance to amoxycillin and amoxycillin in combination with clavulanic acid was related to the specific activity of the TEM-1 beta-lactamase. The variation in specific activity was shown to be related to plasmid type as determined by restriction analysis. No obvious relationship between beta-lactamase specific activity and resistance to amoxycillin and amoxycillin plus clavulanic acid could be demonstrated in the original plasmid donor strains.