Characterization of Acinetobacter chengduensis sp. nov., isolated from hospital sewage and capable of acquisition of carbapenem resistance genes.

Two strains of the genus Acinetobacter, WCHAc060005 ^T and WCHAc060007, were isolated from hospital sewage in China. The two strains showed different patterns of resistance to clinically important antibiotics and their taxonomic positions were investigated. Cells are Gram-negative, obligate aerobic, non-motile, catalase-positive and oxidase-negative coccobacilli. A preliminary analysis based on the 16S rRNA gene sequences indicated that the two strains had the highest similarity to Acinetobacter cumulans WCHAc060092 ^T (99.02%). Whole-genome sequencing of the two strains and genus-wide phylogeny reconstruction based on a set of 107 Acinetobacter core genes indicated that they formed a separate and internally cohesive clade within the genus. The average nucleotide identity based on BLAST and in silico DNA-DNA hybridization values between the two new genomes were 99.77% and 98.7% respectively, whereas those between the two genomes and the known Acinetobacter species were <88.93% and <34.0%, respectively. A total of 7 different genes were found in the two genome sequences which encode resistance to five classes of antimicrobial agents, including clinically important carbapenems, oxyimino-cephalosporins, and quinolones. In addition, the combination of their ability to assimilate gentisate, but not l-glutamate and d,l-lactate could distinguish the two strains from all known Acinetobacter species. Based on these combined data, we concluded that the two strains represent a novel species of the genus Acinetobacter, for which the name Acinetobacter chengduensis sp. nov. is proposed. The type strain is WCHAc060005 ^T (CCTCC AB 2019139=GDMCC 1.1622=JCM 33509).
(Copyright © 2020 Elsevier GmbH. All rights reserved.)