Genomic Comparisons Of Multiresistant Pseudomonas Aeruginosa Isolates Obtained From A Surgical Intensive Care Unit

Objectives: To investigate the genomic differences of multi-drug resistant Pseudomonas aeruginosa and their interrelations with multiresistant evolvement.Methods: Consecutive antimicrobial susceptibility monitoring data of clinical P. aeruginosa strains were analyzed. MICs of 49 P. aeruginosa isolates were mensurated by agar dilution methods. PFGE was performed to determine the genomic discrepancies of multi-drug resistant P. aeruginosa isolates. 16S rDNA and mutL of 8 representative P. aeruginosa isolates were sequenced. Evolutional distances were analyzed with PHYLIP (version 3.65).Results: 1. All consecutive P. aeruginosa strains were resistant to ampicillin, ampicillin/sulbactam and cefotetan, and tne majority of P. aeruginosa strains were resistant to imipenem, ciprofloxacin, levofloxacin, ceftazidime, piperacillin/tazobactam and cefotaxime. 2. Antimicrobial susceptibilities of P. aeruginosa strains were dynamic during monitoring period and with multiform evolutive modes. 3. 85.7% of the P. aeruginosa isolates were resistant to more than 3 kinds of antimicrobial agents, and the multiresistant rates were drop off from 2001 to 2004. 4. Pattern A was the predominant DNA restriction pattern, which accounted for 61.2% (30/49) of total isolates. P. aeruginosa included in this study with pattern A were all sensitive to amikacin and cefepime, while resistant to levofloxacin and meropenem. The Majority of P. aeruginosa with pattern A is sensitive to gentamicin, aztreonam and ceftazidime, while resistant to ciprofloxacin and cefotaxime. Pattern H, P and some A are inclined to possess extremely severe resistance to more than 6 kinds of antibiotics. 5. The structure of PFGE patterns were different in each year. 6. 16S rDNA of 8 representative P. aeruginosa isolates were highly conserved, except for 3 single nucleotide Polymorphisms. 7. The mutL unrooted tree revealed the clonal relatedness and multiresistant characters of P. aeruginosa isolates.Conclusions: 1. Multi-drug resistant P. aeruginosa is the most prevalent opportunistic pathogen that caused antimicrobial chemotherapy invalid, and rapid evolvement from sensitive to multiresistant is hackneyed under clinical empirical antibiotics usage. 2. PFGE Electrophoresis Patterns were interrelated with multiresistant characters of clinical Multi-drug resistant P. aeruginosa, thereby PFGE is an ideal method for analysing and interpreting chromosomal DNA restriction patterns of clinical Multi-drug resistant P. aeruginosa. 3. PFGE Electrophoresis Pattern A was the most prevalent PFGE Electrophoresis Pattern, and P. aeruginosa with Pattern A were generally sensitive to most antibiotics, and it is more likely to evolve towards extreme multi-drug resistant or sporadically all sensitive strains. Majority multi-drug resistances of P. aeruginosa remain with Pattern A are inclined to decrease. 4. P. aeruginosa strains with Patterns otherthan A were the minority P. aeruginosa strains, indicate that those patterns were most likely unstable. P. aeruginosa strains with Pattern H and P were most likely to become extreme multi-drug resistant and those with Pattern I and J were inclined to become sensitive to all antibiotics tested in this study. 5. PFGE combined with Phylogram evolutionary gene tree might be an effective method to monitor and identify multiresistant P. aeruginosa.