[Prevalence of the TEM, SHV and CTX-M families of extended-spectrum beta-lactamases in Escherichia coli and Klebsiella spp at the University Hospital of Santa Maria, State of Rio Grande do Sul]. / Prevalência das famílias TEM, SHV e CTX-M de beta-lactamases de espectro estendido em Escherichia coli e Klebsiella spp no Hospital Universitário de Santa Maria, Estado do Rio Grande do Sul.

In this study, the distribution and prevalence of extended-spectrum beta-lactamases belonging to the TEM, SHV and CTX-M families were estimated among samples of Escherichia coli and Klebsiella spp. at the university hospital of Santa Maria, Rio Grande do Sul. Over a 14-month period, 90 microorganisms were selected as likely ESBL producers. The isolates were subjected to confirmatory phenotype tests for the presence of ESBL. Through investigating the respective genes using the polymerase chain reaction, the ESBL types present in each microorganism were then determined. Fifty-five samples (61.1%) were confirmed as ESBL-positive by means of the combined disc method, and 57 (63.3%) were found to be ESBL producers by means of the double disc method. From the polymerase chain reaction, ESBLs of TEM and SHV types were more frequently present in Klebsiella pneumoniae, while ESBL of CTX-M type was more frequently present in Klebsiella oxytoca.