National Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, Cooperative Innovation Center for Sustainable Pig Production, Huazhong Agricultural University, Wuhan, Hubei, China.
Institute of Animal Husbandry Research, Henan Academy of Agricultural Sciences, Zhengzhou, Henan, China.
Vet Microbiol. 2024 Aug;295:110168. doi: 10.1016/j.vetmic.2024.110168. Epub 2024 Jul 1.
Glaesserella parasuis is an important porcine pathogen that commonly colonizes the upper respiratory tract of pigs and is prone to causing Glässer's disease under complex conditions. As yet, the disease has led to serious economic losses to the swine industry worldwide. Studies so far have found that several virulence factors are associated with the pathogenicity of G. parasuis, but the pathogenic mechanism is still not fully understood. Cytolethal distending toxin (CDT), a potential virulence factor in G. parasuis, is involved in cytotoxicity, serum resistance, adherence to and invasion of host cells in vitro. Here, to further investigate the pathogenic role of CDT during G. parasuis infection in vitro and in vivo, a double cdt1 and cdt2 deletion mutant (Δcdt1Δcdt2) without selectable marker was first generated in G. parasuis JS0135 strain by continuous natural transformations and replica plating. Morphological observation and lactate dehydrogenase assay showed that the Δcdt1Δcdt2 mutant was defective in cytotoxicity. Additionally, the Δcdt1Δcdt2 mutant was more susceptible to phagocytosis caused by 3D4/2 macrophages compared to the wild-type JS0135 strain. Moreover, by focusing on clinical signs, necropsy, bacterial recovery and pathological observation, we found that the deletion of cdt1 and cdt2 genes led to a significant attenuation of virulence in G. parasuis. Taken together, these findings suggest that as an important virulence factor, CDT can significantly affect the pathogenicity of G. parasuis.
副猪嗜血杆菌是一种重要的猪病原体，通常定植于猪的上呼吸道，在复杂条件下易引起格拉泽氏病。迄今为止，该疾病已导致全球养猪业遭受严重的经济损失。目前的研究发现，几种毒力因子与副猪嗜血杆菌的致病性有关，但致病机制仍不完全清楚。细胞致死膨胀毒素（CDT）是副猪嗜血杆菌的一种潜在毒力因子，参与体外细胞毒性、血清抗性、黏附和侵袭宿主细胞。在此，为了进一步研究 CDT 在副猪嗜血杆菌体外和体内感染过程中的致病作用，我们首先通过连续自然转化和复制平板技术，在 JS0135 株中构建了一种无选择标记的双 cdt1 和 cdt2 缺失突变体（Δcdt1Δcdt2）。形态学观察和乳酸脱氢酶测定表明，Δcdt1Δcdt2 突变体在细胞毒性方面存在缺陷。此外，与野生型 JS0135 菌株相比，Δcdt1Δcdt2 突变体更容易被 3D4/2 巨噬细胞吞噬。此外，通过关注临床症状、剖检、细菌回收和组织病理学观察，我们发现 cdt1 和 cdt2 基因的缺失导致副猪嗜血杆菌毒力显著减弱。综上所述，这些结果表明，作为一种重要的毒力因子，CDT 可显著影响副猪嗜血杆菌的致病性。
