Cross-sectional study on fecal carriage of Enterobacteriaceae with resistance to extended-spectrum cephalosporins in primary care patients.

The aim of this study was to gain knowledge of the local epidemiology of extended-spectrum cephalosporin-resistant bacteria in primary care patients in a Swiss community. Fecal swabs were obtained from 291 primary care patients. Phenotyping and genotyping methods were used for further characterization of the isolates. Risk factors associated with carriage of ß-lactam-resistant strains were determined. Extended-spectrum cephalosporin-resistant Enterobacteriaceae were detected in 15 (5.2%) of the primary care patients. Thirteen isolates were CTX-M producers, one produced SHV-12, and three carried CMY-2. The pathogenic pandemic clone Escherichia coli ST131 was detected in 26.6% of the patients. Two patients (13.3%) carried two distinct strains simultaneously. There was a statistically significant risk of carriage of resistant strains for persons with a history of antibiotic therapy 4 months before sampling (p=0.05), markedly for therapy with ß-lactam (p=0.01). Age, gender, or history of hospitalization 4 months before sampling was not a risk factor for the acquisition of resistant bacteria in the analyzed patients. The relatively low prevalence of extended-spectrum cephalosporin-resistant strains in the community reflects the nationwide restrictive policy of antibiotic prescription as well as local implementation thereof. Nevertheless, our study shows that a potent antimicrobial resistance reservoir is present in primary care patients.