Background: The aim of this study was to evaluate the incidence of TEM- and SHV-type extended spectrum betalactamases (ESBLs) in Escherichia coli in a 700-bed teaching hospital between 1994 and 1996.
Material and methods: Strains that presented reduced diameters to third-generation cephalosporins, as identified by disc diffusion techniques, were studied. The betalactamases involved were characterized by determination of the isoelectric point, hydrolysis profile, gene detection by polymerase chain reaction (PCR), and sequencing of the amplified products.
Results: 96 strains (1.4%) out of 7,054 strains of E. coli isolated between 1994 and 1996 showed decreased susceptibility to third-generation cephalosporins and only 4 strains (0.06%) produced ESBLs. Two strains produced SHV-2 and two produced TEM-12.
Conclusions: The contribution of ESBL production to resistance to third-generation cephalosporins was low: 0.06% of all the E. coli strains isolated between 1994 and 1996.