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 patient morbidity and mortality. Materials and Methods: The study included carbapenem-resistant P. aeruginosa isolates recovered from various clinical specimens of 334 patients in Karadeniz Technical University Faculty of Medicine Hospital, a 900-bed university hospital in Trabzon, Turkey. MBL-related carbapenem-resistant PA strains were phenotypically investigated using the Modified Hodge test and the imipenem/imipenem-ethylene diamine tetra acetic acid combined disc tests. Multiplex polymerase chain reaction was used to investigate the presence of blaIMP, blaVIM, blaGIM, blaSIM, and blaSPM genes, which are responsible for MBL production. Clonal relationships among MBL-PA isolates were analyzed by pulsed-field gel electrophoresis. The patients" hospital records were retrospectively examined. Various demographic and clinical characteristics were evaluated in relation to MBL-PA. Results: Thirty-two (9.6%) of the carbapenem-resistant PA isolates were found to carry blaVIM and/or blaIMP, with three strains harboring both blaVIM and blaIMP. MBL-PA isolates were more resistant to aminoglycosides and quinolones. Eight Verona integron-encoded metallo-beta-lactamase-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 inpatients. Compared to non-MBL carbapenem-resistant PA, the risk factors evaluated were found to have no association with MBL-PA. In addition, there was no statistically significant difference in mortality between patients from whom MBL-PA or non-MBL-PA was isolated. Conclusion: Although MBL-PA has been implicated in various healthcare-related outbreaks, no specific risk factor has been identified in association with MBL-PA isolation. To our knowledge, this is the first study in Turkey to detect P. aeruginosa isolates carrying both blaVIM and blaIMP.