Molecular heterogeneity of blaVIM-2-containing integrons from Pseudomonas aeruginosa plasmids encoding the VIM-2 metallo-β-lactamase

A bla(VIM-2) metallo-beta-lactamase determinant, identical to that previously identified in Pseudomonas aeruginosa COL-1 isolate from a French hospital, was detected on a 28-kb plasmid carried by a nosocomial isolate of P. aeruginosa from Verona, Italy. In this plasmid the bla(VIM-2) determinant was inserted into a class 1 integron of original structure, named In72, that contains a partially deleted intI1 integrase gene and two gene cassettes. The first cassette carries an aacA4 aminoglycoside acetyl transferase determinant. The second cassette carries a bla(VIM-2) determinant followed by a partially deleted attC site. The structure of In72 was notably different from that of In56, the bla(VIM-2)-containing integron found in the COL-1 isolate, revealing the existence of molecular heterogeneity among bla(VIM-2)-containing integrons in clinical isolates of P. aeruginosa from Europe.