Species Distribution of Clinical Acinetobacter Isolates Revealed by Different Identification Techniques

A total of 2582 non-duplicate clinical Acinetobacter spp. isolates were collected to evaluate the performance of four identification methods because it is important to identify Acinetobacter spp. accurately and survey the species distribution to determine the appropriate antimicrobial treatment. Phenotyping (VITEK 2 and VITEK MS) and genotyping (16S rRNA and rpoB gene sequencing) methods were applied for species identification, and antimicrobial susceptibility test of imipenem and meropenem was performed with a disk diffusion assay. Generally, the phenotypic identification results were quite different from the genotyping results, and their discrimination ability was unsatisfactory, whereas 16S rRNA and rpoB gene sequencing showed consistent typing results, with different resolution. Additionally, A. pittii, A. calcoaceticus and A. nosocomialis, which were phylogenetically close to A. baumannii, accounted for 85.5% of the non-A. baumannii isolates. One group, which could not be clustered with any reference strains, consisted of 11 isolates and constituted a novel Acinetobacter species that was entitled genomic species 33YU. None of the non-A. baumannii isolates harbored a blaOXA-51-like gene, and this gene was disrupted by ISAba19 in only one isolate; it continues to be appropriate as a genetic marker for A. baumannii identification. The resistance rate of non-A. baumannii isolates to imipenem and/or meropenem was only 2.6%, which was significantly lower than that of A. baumannii. Overall, rpoB gene sequencing was the most accurate identification method for Acinetobacter species. Except for A. baumannii, the most frequently isolated species from the nosocomial setting were A. pittii, A. calcoaceticus and A. nosocomialis.

共计收集2582株非重复的铜绿假单胞菌属临床分离株，旨在评估四种鉴定方法的性能。准确识别铜绿假单胞菌属及其物种分布，以确定合适的抗菌治疗方案至关重要。本研究采用了表型鉴定（VITEK 2及VITEK MS）和基因型鉴定（16S rRNA及rpoB基因测序）方法进行物种鉴定，并使用纸片扩散法对亚胺培南和美罗培南的抗菌敏感性进行测试。通常，表型鉴定结果与基因型鉴定结果存在显著差异，其区分能力不尽人意。然而，16S rRNA和rpoB基因测序显示了一致的分型结果，但分辨率有所不同。此外，与鲍曼不动杆菌亲缘关系较近的克雷伯菌属（A. pittii）、醋酸钙不动杆菌属（A. calcoaceticus）和医院不动杆菌属（A. nosocomialis）占据了非鲍曼不动杆菌分离株的85.5%。一组无法与任何参考菌株进行聚类的11株分离株构成了一个新型的铜绿假单胞菌属，被命名为基因组物种33YU。非鲍曼不动杆菌分离株中无一携带blaOXA-51样基因，且该基因仅在单一菌株中由ISAba19破坏；因此，该基因继续作为鲍曼不动杆菌鉴定的遗传标记。非鲍曼不动杆菌对亚胺培南和/或美罗培南的耐药率仅为2.6%，显著低于鲍曼不动杆菌。总体而言，rpoB基因测序是鉴定铜绿假单胞菌属物种的最准确方法。除了鲍曼不动杆菌外，在医院环境中最常分离到的物种为克雷伯菌属（A. pittii）、醋酸钙不动杆菌属（A. calcoaceticus）和医院不动杆菌属（A. nosocomialis）。