Molecular Epidemiology and Clinical Characteristics of Metallo-Beta-Lactamase Producing Pseudomonas aeruginosa Isolates

Introduction: In this study, we aimed to determine the epidemiological properties of metallo-beta-lactamase producing Pseudomonas aeruginosa (MBL-PA) isolates and to investigate the relationship between the presence of MBL-PA and any association with patient morbidity and mortality. Materials and Methods: Carbapenem-resistant P. aeruginosa strains isolated from several clinical specimens of 334 patients in Farabi Hospital, a 900-bedded university hospital in Trabzon, Turkey were included in the study. MBL-related carbapenem-resistant Pseudomonas aeruginosa (PA) strains were phenotypically investigated by the Modified Hodge test and the imipenem/imipenem-EDTA combined disc tests. The multiplex polymerase chain reaction (multiplex PCR) method was employed in order to investigate the presence of the bla(IMP), bla(VIM), bla(GIM), bla(SIM) and bla(SPM) genes responsible for MBL production. Clonal relationships among MBL-PA isolates were analyzed by PFGE. The hospital records of patients were retrospectively examined. Various demographical and clinical characteristics of patients in relation to MBL-PA were statistically evaluated. Results: Thirty-two (9.6%) of the carbapenem-resistant PA isolates were found to be bla(VIM) and /or bla(IMP) positive. Three of them harbored both bla(VIM) and bla(IMP). MBL-PA isolates were more resistant to aminoglycosides and quinolones. Eight VIM type MBL-PA isolates were found to be identical in adults, while several clonally-related clusters were observed among MBL-PA isolates in both the pediatric and adult in-patients. Compared to non-MBL carbapenem resistant PA, the risk factors evaluated were found to have no association with MBL-PA. Also no statistically significant differences were found between patients from whom MBL-PA or non-MBL-PA was isolated, with respect to mortality. Conclusion: MBL-PA has been found responsible for a variety of healthcare related outbreaks, however no specific risk factor has been found to be related to MBL-PA isolation. Also, to our knowledge, this is the first study in which Pseudomonas aeruginosa isolates co-existing bla(VIM) and bla(IMP) have been detected in Turkey.