Detection of PSE-2 beta-lactamase in enterobacteria.

PSE-2, a plasmid-mediated beta-lactamase which was previously considered pseudomonas specific, was observed in clinical isolates of Escherichia coli, Klebsiella pneumoniae, Providencia stuartii, and Enterobacter cloacae. All four isolates transferred PSE-2 production, together with resistance to gentamicin, tobramycin, kanamycin, and sulfamethoxazole, into Escherichia coli J62-1 and Pseudomonas aeruginosa PU21. Transfer correlated with acquisition by the transconjugants of a 65-megadalton plasmid, and this element was considered to encode PSE-2 expression. The PSE-2 enzyme conferred high-level carbenicillin resistance on both J62-1 and PU21 transconjugants, although the PSE-2-producing Providencia stuartii isolate was susceptible to carbenicillin.