Changing the epidemiology of carbapenem-resistant Pseudomonas aeruginosa in a Brazilian teaching hospital: the replacement of São Paulo metallo-β-lactamase-producing isolates.

In Brazil, carbapenem-resistant Pseudomonas aeruginosa isolates are closely related to the Sao Paulo metallo-beta-lactamase (SPM) Brazilian clone. In this study, imipenem-resistant isolates were divided in two sets, 2002/2003 and 2008/2009, analysed by pulsed field gel electrophoresis and tested for the Ambler class B metallo-beta-lactamase (MBL) genes bla(SPM-1), bla(IMP) and bla(VIM). The results show a prevalence of one clone related to the SPM Brazilian clone in 2002/2003. In 2008/2009, P. aeruginosa isolates were mostly MBL negative, genetically diverse and unrelated to those that had been detected earlier. These findings suggest that the resistance to carbapenems by these recent P. aeruginosa isolates was not due to the spread of MBL-positive SPM-related clones, as often observed in Brazilian hospitals.