Ottawa Research and Development Centre, Agriculture and Agri-Food Canada, 960 Carling Ave., Ottawa, Ontario, K1A 0C6, Canada.
Canadian Food Inspection Agency, Charlottetown, PE, C1A 5T1, Canada.
BMC Genomics. 2022 Jun 27;23(1):471. doi: 10.1186/s12864-022-08663-w.
Emerging pathogenic bacteria are an increasing threat to public health. Two recently described species of the genus Aliarcobacter, A. faecis and A. lanthieri, isolated from human or livestock feces, are closely related to Aliarcobacter zoonotic pathogens (A. cryaerophilus, A. skirrowii, and A. butzleri). In this study, comparative genomics analysis was carried out to examine the virulence-related, including virulence, antibiotic, and toxin (VAT) factors in the reference strains of A. faecis and A. lanthieri that may enable them to become potentially opportunistic zoonotic pathogens.
Our results showed that the genomes of the reference strains of both species have flagella genes (flaA, flaB, flgG, flhA, flhB, fliI, fliP, motA and cheY1) as motility and export apparatus, as well as genes encoding the Twin-arginine translocation (Tat) (tatA, tatB and tatC), type II (pulE and pulF) and III (fliF, fliN and ylqH) secretory pathways, allowing them to secrete proteins into the periplasm and host cells. Invasion and immune evasion genes (ciaB, iamA, mviN, pldA, irgA and fur2) are found in both species, while adherence genes (cadF and cj1349) are only found in A. lanthieri. Acid (clpB), heat (clpA and clpB), osmotic (mviN), and low-iron (irgA and fur2) stress resistance genes were observed in both species, although urease genes were not found in them. In addition, arcB, gyrA and gyrB were found in both species, mutations of which may mediate the resistance to quaternary ammonium compounds (QACs). Furthermore, 11 VAT genes including six virulence (cadF, ciaB, irgA, mviN, pldA, and tlyA), two antibiotic resistance [tet(O) and tet(W)] and three cytolethal distending toxin (cdtA, cdtB, and cdtC) genes were validated with the PCR assays. A. lanthieri tested positive for all 11 VAT genes. By contrast, A. faecis showed positive for ten genes except for cdtB because no PCR assay for this gene was available for this species.
The identification of the virulence, antibiotic-resistance, and toxin genes in the genomes of A. faecis and A. lanthieri reference strains through comparative genomics analysis and PCR assays highlighted the potential zoonotic pathogenicity of these two species. However, it is necessary to extend this study to include more clinical and environmental strains to explore inter-species and strain-level genetic variations in virulence-related genes and assess their potential to be opportunistic pathogens for animals and humans.
新兴的致病性细菌对公共卫生构成日益严重的威胁。最近从人类或牲畜粪便中分离出的弧菌属的两个新描述的种，即粪拟态弧菌和拉氏弧菌，与兽源弧菌病原体（嗜肺军团菌、斯氏弧菌和脆弱拟杆菌）密切相关。在这项研究中，进行了比较基因组学分析，以研究粪拟态弧菌和拉氏弧菌参考菌株中的毒力相关、包括毒力、抗生素和毒素（VAT）因子，这些因子可能使它们成为潜在的机会性病原体。
我们的结果表明，这两个种的参考菌株的基因组都具有鞭毛基因（flaA、flaB、flgG、flhA、flhB、fliI、fliP、motA 和 cheY1）作为运动和外排装置，以及编码双精氨酸易位（Tat）（tatA、tatB 和 tatC）、II 型（pulE 和 pulF）和 III 型（fliF、fliN 和 ylqH）分泌途径的基因，使它们能够将蛋白质分泌到周质和宿主细胞中。侵袭和免疫逃逸基因（ciaB、iamA、mviN、pldA、irgA 和 fur2）在这两个种中都有发现，而粘附基因（cadF 和 cj1349）仅在拉氏弧菌中发现。在这两个种中都观察到酸（clpB）、热（clpA 和 clpB）、渗透压（mviN）和低铁（irgA 和 fur2）应激抵抗基因，尽管它们中没有发现脲酶基因。此外，在这两个种中都发现了 arcB、gyrA 和 gyrB，它们的突变可能介导对季铵化合物（QACs）的抗性。此外，通过 PCR 试验验证了包括 6 个毒力（cadF、ciaB、irgA、mviN、pldA 和 tlyA）、2 个抗生素耐药性[tet（O）和 tet（W）]和 3 个细胞毒素扩张毒素（cdtA、cdtB 和 cdtC）基因在内的 11 个 VAT 基因。拉氏弧菌所有 11 个 VAT 基因均呈阳性。相比之下，粪拟态弧菌除了 cdtB 基因外，其他 10 个基因均呈阳性，因为该种没有针对该基因的 PCR 试验。
通过比较基因组学分析和 PCR 试验在粪拟态弧菌和拉氏弧菌参考菌株的基因组中鉴定毒力、抗生素耐药性和毒素基因，突出了这两个种的潜在人畜共患病毒性。然而，有必要将这项研究扩展到包括更多的临床和环境菌株，以探索种间和菌株水平的毒力相关基因的遗传变异，并评估它们作为动物和人类机会性病原体的潜力。
