[Discovery of new structure of class 1 integron in MDR Pseudomonas aeruginosa and its association with drug-resistance].

OBJECTIVE: To investigate the characteristics of class I integrons among clinical multidrug-resistant Pseudomonas aeruginosa isolates, and to analyze the association between class I integrons and multidrug resistance. METHODS: Pseudomonas aeruginosa strains were isolated from clinical samples, and the multidrug-resistant ones were picked out from these isolates. PCR assays were used to detect the variable regions of class I integrons, and the resulting products were then digested with restriction enzyme Sau 3A I and sequenced. SPSS19.0 software was used for statistical analysis. RESULTS: Class I integrons were detected in 27.3% of the clinical multidrug-resistant Pseudomonas aeruginosa isolates. Amplification of variable regions of class I integrons revealed three different gene cassette arrays (1500, 2300 and 4000 bp), two of them were also found in other bacteria. These gene cassette arrays encoded aminoglycoside-modifying enzymes (aadA, aadB, aac(6') II and aadA13), beta-lactamases (blaCARB8 and oxa10) and chloromycetin efflux pump (cmlA8). Analysis results suggested closely relationship between class I integrons and aminoglycoside resistance. CONCLUSION: We revealed three different gene cassette arrays in the clinical isolates of the multidrug-resistant Pseudomonas aeruginosa, and gene cassette array aadB-aac(6') II -blaCARB8 was the most prevalent. The three gene cassette arrays all contained the aminoglycoside-resistant genes.