Emergence of IntI1 associated blaVIM-2 gene cassettemediated carbapenem resistance in opportunistic pathogen Pseudomonas stutzeri

Carbapenems are considered as the last resort of antibiotic for the treatment of infection but many Gram-negative organisms have developed resistance to this antibiotic through loss or alteration of outer membrane porin protein OprD, over-expression of efflux pump, hyperproduction of an AmpC-type-β-lactamase and/or carbapenemase.1 Carbapenemases are β-lactamases with catalytic efficiencies for carbapenem hydrolysis, including enzymes from Ambler’s classes A (extended spectrum β-lactamase), B (metallo-β-lacatamase, MBL) and D (Oxacillinases, OXA). The serine carbapenemases are derivatives of class A (e.g., IMI, KPC, GES) and class D enzymes (e.g., OXA-23, OXA-40, OXA-48) that hydrolyze carbapenems poorly but able to confer resistance. MBLs (e.g., IMP, VIM, GIM, SPM-l) can hydrolyze all β-lactams, including carbapenems (with the exception of aztreonam).1, 2 Dutch imipenemase (DIM-1), a novel subclass 1 MBL can significantly hydrolyze broad-spectrum cephalosporins and carbapenems.3 IMP and Verona integron-encoded metallo-β-lactamase (VIM) derivatives are widespread MBLs4 and can be harbored within gene cassettes embedded into class 1 integron structure3 as we know integrons can act as expression vector for the genes captured in the cassette.5