New Delhi metallo-β-lactamase (NDM-1)-producing Klebsiella pneumoniae of sequence type ST11: first identification in a hospital of central Italy

The emergence of novel resistant markers hampers the efficacy of beta-lactam antibiotics to treat infections caused by micro-organisms carrying such resistances. This study investigated the antimicrobial susceptibility pattern, the carpapenem-associated determinants and the molecular epidemiology of Klebsiella pneumoniae showing a New Delhi (NDM) metallo-β-lactamase phenotype, isolated from a patient admitted to intensive care unit of the main hospital for acute care of Molise region, central Italy. Antimicrobial susceptibility was assessed for nineteen antibiotics by disc diffusion and agar dilution methods. Carbapenem-associated resistance determinants were detected through gene-specific amplifications, targeting bla_NDM-1, bla_SHV and bla_TEM, bla_CTX-M, bla_KPC, bla_VIM, bla_IMP, bla_GES and bla_OXA-48-lixe. Molecular characterization was carried out through multilocus sequence typing. The strain showed a multidrug resistant profile, and PCR and sequencing confirmed the presence of bla_NDM-1 gene. Among the multiple resistance-associated determinants tested, the isolate, which was assigned to the sequence type ST11, only harboured bla_SHV and bla_TEM genes. This is the first report of NDM-1 variant in the regional healthcare setting for acute patients, raising significant concerns about the increase in the antimicrobials resistance spread through a different mechanism from the endemic KPC carbapenemase, and underlining the circulation of a virulent clone never identified before in this area.