Table_1_Surface-Related Features and Virulence Among Acinetobacter baumannii Clinical Isolates Belonging to International Clones I and II.xlsx

Acinetobacter baumannii currently represents one of the most important nosocomial infection agent due to its multidrug-resistance and a propensity for the epidemic spread. The A. baumannii strains belonging to the international clonal lineages I (IC I) and II (IC II) are associated with the hospital outbreaks and a high virulence. However, the intra and inter lineage-specific features of strains belonging to these most worldwide spread A. baumannii clones are not thoroughly explored. In this study we have investigated a set of cell surface-related features of A. baumannii IC I (n = 20) and IC II (n = 16) lineage strains, representing 30 distinct pulsed-field gel electrophoresis types in the collection of clinical isolates obtained in Lithuanian tertiary care hospitals. We show that A. baumannii IC II strains are non-motile, do not form pellicle and display distinct capsular polysaccharide profile compared with the IC I strains. Moreover, in contrast to the overall highly hydrophobic IC I strains, IC II strains showed a greater variation in cell surface hydrophobicity. Within the IC II lineage, hydrophilic strains demonstrated reduced ability to form biofilm and adhere to the abiotic surfaces, also possessed twofold thicker cell wall and exhibited higher resistance to desiccation. Furthermore, these strains showed increased adherence to the lung epithelial cells and were more virulent in nematode and mouse infection model compared with the hydrophobic IC II strains. According to the polymerase chain reaction-based locus-typing, the reduction in hydrophobicity of IC II strains was not capsule or lipooligosaccharide locus type-dependent. Hence, this study shows that the most widespread A. baumannii clonal lineages I and II markedly differ in the series of cell surface-related phenotypes including the considerable phenotypic diversification of IC II strains at the intra-lineage level. These findings suggest that the genotypically related A. baumannii strains might evolve the features which could provide an advantage at the specific conditions outside or within the host.

鲍曼不动杆菌目前已成为引起医院感染最为重要的病原体之一，这主要归因于其多重耐药性和易于流行的特性。属于国际克隆谱系I（IC I）和II（IC II）的鲍曼不动杆菌菌株与医院爆发病例及高致病性有关。然而，这些在全球范围内广泛传播的鲍曼不动杆菌克隆株的种内和种间谱系特征尚未得到充分研究。在本研究中，我们调查了鲍曼不动杆菌IC I（n = 20）和IC II（n = 16）谱系菌株的细胞表面相关特征，这些菌株代表临床分离株库中的30种不同的脉冲场凝胶电泳类型，该库收集自立陶宛三级护理医院。我们发现，与IC I菌株相比，IC II菌株不具有运动能力，不形成细胞外膜，并显示出独特的荚膜多糖谱。此外，与整体疏水性的IC I菌株相反，IC II菌株在细胞表面疏水性方面表现出更大的变异。在IC II谱系内，亲水性菌株表现出降低的生物膜形成能力和粘附于非生物表面的能力，其细胞壁厚度是亲水性菌株的两倍，并显示出更高的耐旱性。此外，这些菌株对肺上皮细胞的粘附性增加，与疏水性IC II菌株相比，在蠕虫和小鼠感染模型中表现出更高的致病性。根据基于聚合酶链反应的位点分型，IC II菌株疏水性的降低并非依赖于荚膜或脂寡糖位点类型。因此，本研究表明，最广泛传播的鲍曼不动杆菌克隆谱系I和II在一系列细胞表面相关表型上存在显著差异，包括IC II谱系内显著的表型多样性。这些发现表明，基因型相关的鲍曼不动杆菌菌株可能会进化出在宿主外部或内部特定条件下具有优势的特征。