Detection of Pseudomonas aeruginosa carried a new array of gene cassettes within class 1 integron isolated from a teaching hospital in Nanjing, China.

We report here novel array of gene cassettes found in single variable region of class 1 integron disseminated in Pseudomonas aeruginosa isolated from a teaching hospital in Nanjing, Jiangsu Province, China. 29 of 47 (61%) P. aeruginosa strains were confirmed haboured class 1 integron, and all the positive strains have the same variable region confirmed by PCR and RFLP methods. The variable region contained an unreported order of four gene cassettes aac(6')-II-aadA13-cmlA8-oxa-10. Of those, cmlA8 gene was a variant of cmlA5 encoding non-enzymatic protein which putatively confer resistance to chloramphenicol. Susceptibility testing revealed multidrug-resistant mechanisms were involved in the class 1 integron positive clinical isolates. And the class 1 integron located on an about 15 kb transferable plasmid was certified by conjugation experiment and plasmid DNA analysis. The macro restriction profile indicated those clinical strains were clonally related.