Exposure to co-amoxiclav as a risk factor for co-amoxiclav-resistant Escherichia coli urinary tract infection.

The objective of the study was to define whether individual exposure to co-amoxiclav is a risk factor for selecting co-amoxiclav-resistant Escherichia coli in vivo. One hundred and eight patients were included in our study as soon as they were found to have a urinary tract infection (UTI) due to E. coli. Stool probes were also undertaken for some of these patients. Co-amoxiclav administration in the month before diagnosing the UTI, and any treatment to cure the current UTI were recorded for all patients. When co-amoxiclav-resistant E. coli was detected in the stools after diagnosis of E. coli UTI, isolates were compared with urinary E. coli isolates in terms of clonal relatedness, beta-lactam susceptibility and mechanisms of beta-lactam resistance. The patients who had taken co-amoxiclav in the month before the reported E. coli UTI had a significantly higher risk of being infected with co-amoxiclav-resistant E. coli. Those patients treated with amoxicillin for a current infection were at greater risk of intestinal carriage of co-amoxiclav-resistant E. coli; those treated with co-amoxiclav had a greater risk of intestinal carriage of co-amoxiclav-resistant Gram-negative bacilli than patients treated with third-generation cephalosporins or fluoroquinolones. Hence, individual exposure to co-amoxiclav is a risk factor for UTIs caused by co-amoxiclav-resistant E. coli or for carrying co-amoxiclav-resistant Gram-negative bacilli in the digestive tract.