Mutation of Pseudomonas aeruginosa specifying reduced affinity for penicillin G.

A mutant of Pseudomonas aeruginosa strain PAO503 was isolated after ethane-methane-sulfonate mutagenesis and selection of ticarcillin. The mutant, PCC17, displayed reduced affinity for [14C] penicillin G at all of its penicillin-binding proteins as well as a general increase in resistance to all the beta-lactam antibiotics tested. The mutation designated pbpA has been mapped by FP-2-mediated conjugation and was located distal to the proA locus and 33% linked to it. The two loci were not cotransducible with phage F116L. PCC17 and exconjugants produced from it had similar phenotypes, displayed the reduced affinity for [14C] penicillin G, had similar resistance profiles, and had an increased amount of protein corresponding to penicillin-binding protein 6. On back mutation the pbpA locus reverted to the PAO503 phenotype.