Molecular Identification of Extended-Spectrum--Lactamase Genes from Enterobacteriaceae Isolated from Healthy Human Carriers in Switzerland

In this study, fecal samples from 586 healthy humans were investigated to determine the occurrence of extended-spectrum--lactamase (ESBL)-producing Enterobacteriaceae in Swiss people. A total of 5.8 % of the human fecal samples yielded ESBL pro-ducers, and all of the 34 isolated strains were Escherichia coli. PCR analysis revealed that 14 strains produced CTX-M-15, 10 pro-duced CTX-M-1, 7 strains produced CTX-M-14, and 2 strains produced CTX-M-2 ESBLs. One strain produced SHV-12 ESBL. Of the 34 isolates, 15 produced additional TEM-1 broad-spectrum -lactamases. By serotyping, a high degree of diversity among the strains was found. Antimicrobial resistance in bacteria has emerged as a problemin both human and veterinarymedicine. One of the currently most important resistance mechanisms in Enterobacteriaceae, which reduces the efficacy even of modern expanded-spectrum cephalosporins (except cephamycins and carbapenems) and monobactams, is based on plasmid-mediated production of extended-spectrum -lactamases (ESBL). Until now, more than 600 ESBL variants are known. Among them, the over 100 CTX-M enzymes so far reportedmay be grouped into fivemain subgroups (3). As a matter of growing concern, resistance caused by ESBLs i