CTX-M-1-related extended-spectrum beta-lactamases producing Escherichia coli: so far a sporadic event in Western Austria.

Background: The present study was aimed to searching for CTX-M-type extended-spectrum beta-lactamases in community- and hospital-acquired Escherichia coli (E. coli) collected in western Austria and to investigate their clonal relatedness and their ability to spread.

Patients And Methods: All patients with E. coli positive cultures collected from a catchment population of 186,000 between January and July 2006 were enrolled into the study. CTX-M-producing E. coli were identified by antibiotic susceptibility testing and blaCTX-M multiplex PCR. Clonal relatedness was analyzed by pulsed-field gel electrophoresis (PFGE).

Results: In 2,042 E. coli isolates, 20 isolates (16 from urine, 4 from blood cultures) demonstrated CTX-M-1-related genes and no CTX-M-2- or CTX-M-9-related enzymes or CTX-M-15-producing strains were identified. We did not find clonal relatedness among CTX-M-1 producers isolated from the same referring center. E. coli were investigated for plasmid transfer ability of CTX-M-1-encoding genes. Plasmid digest patterns were not consistent with episomal spread of resistance loci. Transfection of CTX-M-encoding plasmids failed.

Conclusion: Our data suggest that the emergence of CTX-M-1-producing E. coli in western Austria may be attributed to multiple independent events.