猪链球菌可引起猪和人类的严重感染。猪的扁桃体是猪链球菌的主要生态位,在同一扁桃体中可以发现不同血清型的猪链球菌。猪链球菌对猪扁桃体的定植被认为是人和猪的重要感染源。然而,猪链球菌如何争夺稳定的扁桃体生态位还不得而知。这里,我们发现猪链球菌菌株WUSS351,从健康的猪扁桃体中分离出来,具有毒性和多重耐药性。ABC运输系统SstFEG,赋予对杆菌肽的抗性,据报道,在体内赋予竞争生存优势。此外,菌株WUSS351有几种抗菌系统,包括新型VII型分泌系统(T7SS),抗生素细菌素,和乳球菌972样细菌素Lcn351。细菌竞争实验证明了T7SS介导的猪链球菌的细胞接触依赖性拮抗作用。培养非依赖性和培养依赖性猪扁桃体微生物组的抗菌活性分析和16SrRNA基因测序表明,Lcn351主要针对猪链球菌,猪扁桃体中的核心微生物群之一。一起来看,我们的研究结果揭示了猪链球菌在扁桃体生态位稳定持续存在的机制,这可能对猪链球菌流行病学有重要意义,潜在影响菌株流行和疾病进展。
Streptococcus suis can cause severe infections in pigs and humans. The tonsils of pigs are major niches for S. suis, and different serotypes of S. suis can be found in the same tonsil. Pig tonsil colonization by S. suis is believed to be an important source of infection for humans and pigs. However, how S. suis competes for a stable tonsil niche is unknown. Here, we found that S. suis strain WUSS351, isolated from a healthy pig tonsil, is virulent and multidrug-resistant. The ABC transporter system SstFEG, conferring resistance to bacitracin, was reported to confer a competitive survival advantage in vivo. In addition, strain WUSS351 has several antimicrobial systems, including a novel type VII secretion system (T7SS), lantibiotic bacteriocin, and lactococcin972-like bacteriocin Lcn351. Bacterial competition experiments demonstrated T7SS-mediated cell contact-dependent antagonism of S. suis. Antibacterial activity analysis and 16S rRNA gene sequencing of the culture-independent and culture-dependent pig tonsillar microbiome revealed that Lcn351 mainly targets S. suis, one of the core microbiomes in pig tonsils. Taken together, our results revealed the mechanism of the stable persistence of S. suis in the tonsil niche, which might have important implications for S. suis epidemiology, potentially influencing strain prevalence and disease progression.