Characterization of defective beta-lactamase genes in Yersinia enterocolitica.

Objectives: To study at the molecular level the heterogeneity of expression of the two chromosomal beta-lactamases, BlaA and BlaB, in Yersinia enterocolitica strains isolated from clinical samples.

Methods: MIC determination by the agar dilution method and beta-lactamase assays was performed to determine the resistance level conferred by these enzymes. DNA cloning, PCR and direct sequencing were used to detect the presence of mutations.