Pseudomonas aeruginosa strain isolated in France that carries a plasmid determining carbenicillin resistance.

A plasmid, R56Be, derived from a clinical strain of Pseudomonas aeruginosa isolated in France in 1973 has been studied. This plasmid confers resistance only to carbenicillin, and although freely transferable between unrelated strains of P. aeruginosa, its transfer from P. aeruginosa to Escherichia coli K-12 was undetectable. R56Be could not be isolated as covalently closed circular deoxyribonucleic acid, but the plasmid could be transduced intact by phage F116L. This suggests that its molecular weight does not exceed that of the phage genome (ca. 40 x 10(6)). In terms of its interaction with male and female sex-specific phages, its exclusion characteristics, and the main properties of beta-lactamase determined by them, R56Be is similar to the previously characterized plasmid RP1-1.