Characterization of a novel acinetobacter bereziniae subspecies harboring blaSIM-1 metallo-ß-lactamase gene

Abstract

Acinetobacter species are aerobic, oxidase negative, non-motile, and non-fermentative gram-negative coccobacilli. They are widely distributed in nature and in the hospital environment and are the second most common non-fermenter among human clinical specimens. At present, 15 Acinetobacter nomenspecies have been isolated in humans. carbapenems are the last resort for the infection by nearly all Acinetobacter spp. isolates. However, carbapenem resistant Acinetobacter isolates that produce metallo-β-lactamases (MBLs) or OXA carbapenemases have been increasingly reported worldwide. We isolated an Acinetobacter strain YMC79 with the blaSIM-1 gene, collected from an oral specimen of a patient diagnosed with acute myeloid leukemia, and it was unidentifiable using conventional biochemical tests. Phylogenetic analysis based on each targeted gene sequence, including 16S rRNA, RNA polymerase ß-subunit gene (rpoB), gyrase B (gyrB) and 16S-23S rRNA gene intergenespacer (ITS) genes indicated that the strain YMC79 was closely related to A. bereziniae, with 98.9%, 96.8%, 91.0%, and 95.9% sequence similarity, respectively. In Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) analysis, spectrums from the strain YMC79 showed specific signals at 5903.5, 6243.2 and 7176.3 m/z (the mass to charge ratio). Major fatty acids were C18 : 1 w9c (34.1%), summed feature 3 (23.4%), C16 : 0 (23.9%) and DNA G+C content 41.2 mol%. The strain YMC79 were clearly different from A. bereziniae and A. guillouiae species by phenotypical characteristics including utilization of D-arabinose, D-ribose, D-xylose, L-xylose, D-adonitol, D-mannose, D-melibiose, xylitol, D-fucose and malonate. In spite of the overall difference, the DNA–DNA relatedness between the strain YMC79 and A. bereziniae KTCT 1268 was 72%. Herein, we report a novel seouli subspecies with blaSIM-1 gene and its phenotypical characteristics.