Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Saudi Arabia.
Department of Microbiology and Immunology, College of Medicine, Alfaisal University, Riyadh, Saudi Arabia.
Front Cell Infect Microbiol. 2024 Apr 22;14:1377993. doi: 10.3389/fcimb.2024.1377993. eCollection 2024.
Detailed assessment of the population structure of group B (GBS) among adults is still lacking in Saudi Arabia. Here we characterized a representative collection of isolates from colonized and infected adults.
GBS isolates (n=89) were sequenced by Illumina and screened for virulence and antimicrobial resistance determinants. Genetic diversity was assessed by single nucleotide polymorphisms and core-genome MLST analyses.
Genome sequences revealed 28 sequence types (STs) and nine distinct serotypes, including uncommon serotypes VII and VIII. Majority of these STs (n=76) belonged to the human-associated clonal complexes (CCs) CC1 (33.71%), CC19 (25.84%), CC17 (11.24%), CC10/CC12 (7.87%), and CC452 (6.74%). Major CCs exhibited intra-lineage serotype diversity, except for the hypervirulent CC17, which exclusively expressed serotype III. Virulence profiling revealed that nearly all isolates (94.38%) carried at least one of the four alpha family protein genes (i.e., , , , and ), and 92.13% expressed one of the two serine-rich repeat surface proteins Srr1 or Srr2. In addition, most isolates harbored the pilus island (PI)-2a alone (15.73%) or in combination with PI-1 (62.92%), and those carrying PI-2b alone (10.11%) belonged to CC17. Phylogenetic analysis grouped the sequenced isolates according to CCs and further subdivided them along with their serotypes. Overall, isolates across all CC1 phylogenetic clusters expressed Srr1 and carried the PI-1 and PI-2a loci, but differed in genes encoding the alpha-like proteins. CC19 clusters were dominated by the III///PI-1+PI-2a (43.48%, 10/23) and V///PI-1+PI-2a (34.78%, 8/23) lineages, whereas most CC17 isolates (90%, 9/10) had the same III///P1-2b genetic background. Interestingly, genes encoding the CC17-specific adhesins HvgA and Srr2 were detected in phylogenetically distant isolates belonging to ST1212, suggesting that other highly virulent strains might be circulating within the species. Resistance to macrolides and/or lincosamides across all major CCs (n=48) was associated with the acquisition of (62.5%, 30/48), (27.1%, 13/48), (8.3%, 4/48), and (2.1%, 1/48) genes, whereas resistance to tetracycline was mainly mediated by presence of (64.18%, 43/67) and (20.9%, 14/67) alone or in combination (13.43%, 9/67).
These findings underscore the necessity for more rigorous characterization of GBS isolates causing infections.
在沙特阿拉伯，关于 B 群（GBS）成年人人群结构的详细评估仍然缺乏。在这里，我们对定植和感染的成年人群中分离出的代表性菌株进行了特征描述。
通过 Illumina 对 GBS 分离株（n=89）进行测序，并筛选毒力和抗微生物药物耐药性决定因素。通过单核苷酸多态性和核心基因组 MLST 分析评估遗传多样性。
基因组序列揭示了 28 个序列型（ST）和 9 个不同的血清型，包括罕见的血清型 VII 和 VIII。这些 ST 中的大多数（n=76）属于与人类相关的克隆群（CC）CC1（33.71%）、CC19（25.84%）、CC17（11.24%）、CC10/CC12（7.87%）和 CC452（6.74%）。除了高度毒力的 CC17 之外，主要的 CC 表现出种内血清型多样性，CC17 仅表达血清型 III。毒力分析显示，几乎所有分离株（94.38%）至少携带四种 alpha 家族蛋白基因中的一种（即、、、和），并且 92.13%表达两种丝氨酸丰富重复表面蛋白 Srr1 或 Srr2 中的一种。此外，大多数分离株携带单独的菌毛岛（PI）-2a（15.73%）或与 PI-1 组合（62.92%），单独携带 PI-2b 的分离株（10.11%）属于 CC17。系统发育分析根据 CC 和进一步根据它们的血清型对测序分离株进行分组。总体而言，所有 CC1 系统发育群的分离株都表达 Srr1 并携带 PI-1 和 PI-2a 基因座，但在编码 alpha 样蛋白的基因上存在差异。CC19 群主要由 III///PI-1+PI-2a（43.48%，10/23）和 V///PI-1+PI-2a（34.78%，8/23）谱系主导，而大多数 CC17 分离株（90%，9/10）具有相同的 III///P1-2b 遗传背景。有趣的是，在属于 ST1212 的系统发育上遥远的分离株中检测到编码 CC17 特异性粘附素 HvgA 和 Srr2 的基因，这表明其他高毒力菌株可能在种内循环。所有主要 CC（n=48）对大环内酯类和/或林可酰胺类的耐药性与获得（62.5%，30/48）、（27.1%，13/48）、（8.3%，4/48）和（2.1%，1/48）基因有关，而对四环素的耐药性主要由单独存在（64.18%，43/67）和（20.9%，14/67）或联合存在（13.43%，9/67）介导。
这些发现强调了对引起感染的 GBS 分离株进行更严格特征描述的必要性。
