[Development of multi-drug resistant mutants of clinical isolates of Pseudomonas aeruginosa after exposure to fluoroquinolone].
Eight multi-drug resistant mutants (4.94%) were found in 162 clinical isolates of P. aeruginosa after exposure to norfloxacin at different concentrations (1/4, 1/2, 1, 2 and 4 MICs) and were investigated for the mechanisms of drug resistance. All the mutants were eight-times more resistant to norfloxacin than the respective parents, and showed the cross-resistance to the other fluoroquinolones. However, these mutants differed in the drug-resistant patterns; the 94-74 mutant was resistant to carbenicillin, ceftazidime and chloramphenicol, TA-15 mutant was resistant to imipenem, and the 93-183 was resistant to carbenicillin, ceftazidime and gentamicin. TA-16 mutant only showed a marked decrease in the bacterial uptake of norfloxacin. Profiles of the outer membrane proteins of the mutants were analyzed by SDS-PAGE method. The six mutants, except for TA-52 and 93-183 mutants, increased the intensity of bands in the 46 KD region. Three mutants (TA-15, TA-16 and 93-183) decreased the intensity of 44 KD (OMPE) and also the former two decreased the intensity of 22 KD (OMP G). The gryA mutations associated with fluoroquinolone-resistance were investigated for the eight mutants, and the 93-183 mutant showed to have the gyrA mutation caused by the alteration in the amino acid sequence of gyrA; Thr-83 (ACC) to Ile (ATC). The result of the present study indicate that multi-drug resistance of clinical isolates of P. aeruginosa develops through different types of mechanisms, and is not easily explained fully by the present results, and suggest that many factors attributed to the development of the resistances in those mutants remains to be clarified.
Hasegawa
M
M
Chemotherapy Division, Mitsubishi Kagaku Bio Clinical Laboratories, Inc.
Kobayashi
I
I
Saika
T
T
Shimadzu
M
M
Nishida
M
M
D000890:Anti-Infective Agents / Q000494:pharmacology*; D004352:Drug Resistance, Microbial / Q000235:genetics; D018432:Drug Resistance, Multiple / Q000235:genetics*; D006801:Humans; D009154:Mutation; D009643:Norfloxacin / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics*
D000890:Anti-Infective Agents; D009643:Norfloxacin