Intercontinental Dissemination of IMP-13-Producing Pseudomonas aeruginosa Belonging in Sequence Type 621

IMP-type metallo-β-lactamases (MBLs) were the first acquired MBLs detected in Gram-negative pathogens, in the early 1990s, and are among the most relevant due to their worldwide distribution (12, 18). Several IMP-type variants have been described (3). IMP-13 was first detected in clinical isolates of Pseudomonas aeruginosa from Italy (16), where IMP-13 has become a widespread carbapenem resistance determinant, even involved in relatively large outbreaks (11, 13, 17). IMP-13 was also occasionally detected in P. aeruginosa isolates from other European countries, including Austria (7), Romania (9), and France (6). Interestingly, the IMP-13-producing Italian isolates were found to belong in the same clonal lineage (13), and a clonal relationship with this lineage was also demonstrated for a Romanian isolate (9). In these isolates, the bla IMP-13 gene was found to be carried in different class 1 integron structures (InPSG, In88, and In89), usually located on the chromosome or, more rarely, on plasmids (11, 13, 16).