Comparison of frequency of imi-r resistant Pseudomonas aeruginosa mutants generated by infection with various bacteriophages-transposons

We compared the frequencies of imipenem-resistant (imi-r) mutants of a Pseu domonas aeruginosa laboratory strain PAO1 infected by the phages-transposon s (PT) specific for this pseudomonade species. The frequency of imi-r mutan ts among the lysogenic bacteria that appeared after infection reflects the frequency of integrative (conserved) PT transposition into ompD2 gene respo nsible for synthesis of porin, the protein required for the passage of anti biotic through the cell membrane. After infection by either PT the proporti on of imi-r mutants among the lysogenic bacteria was higher than that of sp ontaneous mutants. The imi-r mutants induced by PT infection form colonies that differ in morphology when grown on different media. The frequencies of imi-r mutants induced by all PT are similar, except for HW12, PM57, and PM 62 assigned to a species of the group B3. The phages of this species induce imi-r mutants at a high frequency. Variations in frequencies and colony mo rphology of imi-r mutants are discussed.