The mutLMutation in Pseudomonas aeruginosaIsolates Reveals Multidrug-resistant Traits and Possible Evolutionary Trends

To evaluate the genetic differences and possible evolutionary trends of clinical multidrug-resistant (MDR) strains, Pseudomonas aeruginosaisolates were characterized by pulsed-field gel electrophoresis (PFGE) and evolutionary distances were estimated. A total of 85.7% of the P. aeruginosaisolates were MDR strains. Strains with the PFGE pattern A predominated; all were susceptible to amikacin and cefepime but resistant to levofloxacin and meropenem (except strain PA45 which was sensitive to meropenem). PFGE pattern H or P strains exhibited resistance to six to eight different antibiotics. PFGE pattern I or J strains were susceptible to all antibiotics tested. Two imperfect six base-pair tandem repeats, CTGGCG and CTGGCC, were found in the mutLgene. In conclusion, MDR characteristics and PFGE profiles were clearly correlated with the mutLphylogenetic tree. This indicates that mutations in mutLmight contribute to genetic stability in adaptation by changing the MDR traits. Phylogenetic analysis of mutLrevealed the MDR relatedness of P. aeruginosastrains.