Unusual Diversity of Acquired β-lactamases in Multidrug-ResistantPseudomonas aeruginosaIsolates in a Mexican Hospital

Abstract

To investigate the presence of extended spectrum and metallo β-lactamases (MBLs) in Pseudomonas aeruginosa isolates which are resistant to imipenem and ceftazidime that were isolated in a hospital in Mexico. Pulsed-field gel electrophoresis (PFGE) revealed the presence of four clonal types among the 14 isolates. All these genes were found either alone or simultaneously in the P. aeruginosa strains in the following five different arrangements: <bla(GES-5)>; <bla(GES-5), bla(VIM-11)>; <bla(GES-5), bla(VIM-2), bla(VIM-11)>; <bla(GES-5), bla(OXA-2)>; and <bla(GES-5), bla(VIM-2), bla(VIM-11), and bla(OXA-2)>. Class 1 integrons were detected and contained the cassettes bla(GES-5) and bla(OXA-2), but not that of bla(VIM). bla(VIM) genes occurred only in the chromosome, while bla(GES-5) was located in the chromosome and in the plasmids. To our knowledge, this is the first description of P. aeruginosa strains simultaneously producing the VIM-2 and VIM-11 variants, and the combination of GES-5 and MBL carbapenemases, which determines a major challenge for the clinical microbiology laboratory and a remarkable epidemiological risk for the nosocomial spread of multidrug-resistant determinants.