New plasmid-mediated oxacillin-hydrolyzing beta-lactamase in Pseudomonas aeruginosa.

A novel type of oxacillin-hydrolyzing beta-lactamase, termed OXA-4, has been detected in three Pseudomonas aeruginosa strains isolated in Paris between 1977 and 1981. The strains contained similar plasmids that determined resistance to carbenicillin, chloramphenicol, gentamicin, kanamycin, streptomycin, sulphonamide, tetracycline, tobramycin, sodium borate, and mercuric chloride, had a size of approximately 150 megadaltons, and belonged to the P-5 incompatibility group. Compared to reference OXA-1 beta-lactamase produced by plasmid RGN238, OXA-4 beta-lactamase produced by these plasmids had a similar substrate profile, similar response to inhibitors, and identical immunological reactions but differed in isoelectric point. In a more recent survey of 10 French hospitals plasmid-determined OXA-4 beta-lactamase production was found in P. aeruginosa isolates from four hospitals in the Paris area.