Streptococcus suis (S. suis) is an emerging zoonotic pathogen that can cause meningitis, arthritis, pneumonia, and sepsis. It poses a serious threat to the swine industry and public health worldwide. Ornithine carbamoyltransferase (OTC) is involved in the arginine deiminase system. OTC, which is a widely distributed enzyme in microorganisms, mammals, and higher plants, catalyzes the conversion of ornithine to citrulline. The present study showed that the otc gene plays an important role in the pathogenesis of S. suis infections. The ability of an otc-deficient mutant (Δotc) to form a biofilm was significantly reduced compared to the wild-type (WT) strain, as determined by crystal violet staining. Confocal laser scanning microscopy and scanning electron microscopy observations showed that the weakening of biofilm formation by the Δotc strain is related to a decrease in the extracellular matrix. In addition, compared to the WT strain, the Δotc strain had a reduced capacity to adhere to human laryngeal epidermoid carcinoma (HEp-2) cells compared to the WT strain. A real-time PCR analysis showed that the expression of adhesion-related genes by the Δotc strain was also lower than that of the WT strain. The virulence of the Δotc strain was significantly lower than that of the WT strain in a murine infection model. In addition, a histological analysis showed that the pathogenicity of the Δotc strain was lower than that of the WT strain, causing only slight inflammatory lesions in lung, liver, spleen, and kidney tissues. No significant differences were observed between the complemented mutant (CΔotc) and WT strains with respect to biofilm formation, adhesion, gene expression, and virulence. The present study provided evidence that the otc gene plays a pivotal role in the regulation of S. suis adhesion and biofilm formation. It also suggested that the otc gene is indirectly involved in the pathogenesis of S. suis serotype 2 infections.

猪链球菌（猪链球菌）是一种新兴的人畜共患病原体，可引起脑膜炎，关节炎，肺炎和败血症。它对全世界的养猪业和公共卫生构成了严重威胁。鸟氨酸氨基甲酰基转移酶（OTC）参与精氨酸脱亚氨酶系统。OTC是微生物，哺乳动物和高等植物中广泛分布的酶，可催化鸟氨酸向瓜氨酸的转化。本研究表明，otc基因在猪链球菌感染的发病机理中起着重要作用。的能力OTC缺陷型突变体（Δ OTC通过结晶紫染色确定，与野生型（WT）菌株相比，形成生物膜的生物活性显着降低）。共聚焦激光扫描显微镜和扫描电子显微镜观察表明，Δotc菌株对生物膜形成的减弱与细胞外基质的减少有关。此外，与WT株相比，Δotc株与人喉表皮样癌（HEp-2）细胞的粘附能力降低。实时PCR分析表明，Δotc菌株的粘附相关基因的表达也低于WT菌株。Δotc的毒力在鼠感染模型中，该菌株显着低于野生型菌株。此外，组织学分析表明，Δotc菌株的致病性低于WT菌株，仅在肺，肝，脾和肾组织中引起轻微的炎性病变。补充的突变体（CΔ之间没有观察到差异显著OTC）和WT菌株相对于生物膜形成，粘附性，基因的表达，和毒力。本研究提供的证据表明，otc基因在猪链球菌粘附和生物膜形成的调节中起着关键作用。提示otc基因间接参与猪链球菌的发病机制。 血清型2感染。