Coexistence of blaOXA-23 with blaNDM-1 and armA in clinical isolates of Acinetobacter baumannii from India.

摘要: Sir, The production of carbapenemases is the most common mechanism responsible for carbapenem resistance in Acinetobacter baumannii. They include metallo-b-lactamases (VIM, IMP and SIM types), which have been sporadically reported some parts world, acquired OXA-type more frequently identified worldwide are clustered three major subfamilies (blaOXA-23, blaOXA-24 blaOXA-58). 1 High levels to aminoglycosides due plasmid-encoded 16S rRNA methylase Enterobacteriaceae, Pseudomonas aeruginosa spp. documented since 2003. present study was undertaken determine resistance. Three carbapenem-non-susceptible A. baumannii were isolated from patients intensive care unit a tertiary hospital Chennai, India April 2010. Species identification antibiotic testing carried out using an automated machine (VITEK-2). MICs carbapenems determined CLSI agar dilution method, while tigecycline EUCAST broth microdilution method. All isolates resistant all b-lactams, quinolones, only susceptible colistin. Double disc synergy test (DDST) modified Hodge (MHT) used detection other carbapenemases, respectively. PCR screening performed -24, -51 -58-like) known metallo-b-lactamase genes. 3 – 5 showed positivity both DDST MHT, yielded products with expected sizes blaOXA-51, 23-like blaNDM-1 (Table 1). Sequencing blaOXA-23 genes 100% identities previously In isolates, gene adjacent insertion element ISAba1, provides promoter required expression linked genes; blaOXA-51-like also found but not activated by ISAba1. Conjugation experiments Escherichia coli J53 as recipient unsuccessful. Plasmids Enterobacteriaceae detected among PCR-based replicon typing. Susceptibility increased unusual phenotype broad-spectrum high-level aminoglycosides, including amikacin, gentamicin, netilmicin tobramycin (MICs.256 mg/L), susceptibility (MIC1⁄40.5–1 mg/L). methylase-encoding (armA, rmtA, rmtB, rmtC, rmtD npmA). 9 armA NDM-1 metallo-b-lactamase-mediated has many India. However, our knowledge, this first