nfxC-type quinolone resistance in a clinical isolate of Pseudomonas aeruginosa

Quinolone resistance gene nqr-T91 in a clinical isolate of Pseudomonas aeruginosa P1481 was cotransducible with catA1 in P. aeruginosa PAO. The nqr-T91 transductant, PKH-T91, was resistant to norfloxacin, imipenem, and chloramphenicol and showed less norfloxacin accumulation than the parent strain did. Loss of the 46-kDa outer membrane protein (D2) and an increase in the 50-kDa outer membrane protein in PKH-T91 were observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Lipopolysaccharides in the transductant were also changed. These alterations were considered to be related to lower levels of norfloxacin accumulation in PKH-T91. These genetic and biochemical properties suggested that an nfxC type of quinolone-resistant mutation occurred in a clinical isolate of P. aeruginosa P1481.