Analysis of the beta-lactam resistance phenotypes of Escherichia coli. An 8-year survey conducted in Greece.

There have been few studies, outside of France, on the resistance of Escherichi coli to beta-lactams by means of resistance phenotypes. In the present 8-year study from a tertiary Greek hospital, a statistically significant decrease in wild-type strains was noted, with a parallel increase in strains producing penicillinase. Of the total 6,089 isolates analyzed, 62.47% had no acquired resistance mechanisms while 35.70% produced penicillinase, 0.61% cefalosporinase and 0.94% extended-spectrum beta-lactamase. No overexpression of chromosomal cephalosporinase or synthesis of inhibitor-resistant enzymes was found. A shift in the pattern of penicillinase production was noted as, in the early years of the study, intermediate- and high-level penicillinase predominated whereas, in later years, low-level penicillinase prevailed.