Institute of Animal Husbandry and Veterinary Science, Anhui Academy of Agricultural Sciences, Livestock and Poultry Epidemic Diseases Research Center of Anhui Province, Anhui, China; Anhui Province Key Laboratory of Livestock and Poultry Product Safety Engineering, Anhui, China.
Key Laboratory of Animal Physiology and Biochemistry, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China.
Infect Genet Evol. 2021 Jun;90:104768. doi: 10.1016/j.meegid.2021.104768. Epub 2021 Feb 13.
Klebsiella variicola is a widespread opportunistic pathogen that causes infections in humans and animals. Herein a novel Klebsiella strain, AHKv-S01, was isolated and identified from dead chicken embryos in Anhui, China. Its genome contained a circular chromosome of 5,505,304 bp, with 5244 protein-coding genes, and an integrative conjugative element region containing 79 ORF sequences. AHKv-S01 was given a new sequence type number-174. Phylogenetic analyses showed that rpoB partial nucleotide sequences were highly reliable for identifying Klebsiella spp. Most of the 340 unique genes of AHKv-S01 were involved in cell envelop biogenesis, transcription, transport, and metabolic processes. Moreover, AHKv-S01 was sensitive to several antibiotics, but it showed strong resistance to penicillins, macrolides, and lincosamide. The genome contained three drug efflux pump superfamilies, β-lactamase genes, and fosfomycin resistance-related genes. Most drug resistance genes showed amino acid mutations. Multiple virulence and pathogenic factors were also identified, and they were mainly related to adhesion, secretion, iron acquisition, and immune evasion. Chicken embryo lethality assay results revealed that the 7-day chicken embryo lethality rate was 80%, 40%, and 50% for AHKv-S01, K. pneumoniae ATCC10031, and K. pneumoniae CICC24714, respectively. The median lethal dose of AHKv-S01 was 39.9 CFU/embryo. Even low infection levels of AHKv-S01 caused a significant reduction in chicken embryo hatchability. Severe pathological changes to the liver, heart, and brain tissues of embryos infected with AHKv-S01 were observed, and these changes appeared earlier in the heart and brain than in the liver. To conclude, our results provide a foundation for further studies aiming to assess the potential risk of K. variicola to poultry populations and production yields.
阿克沙基氏菌是一种广泛存在的机会致病菌，可引起人类和动物感染。本研究从中国安徽死亡鸡胚中分离到一株新型阿克沙基氏菌，命名为 AHKv-S01。其基因组为 5,505,304bp 的环状染色体，包含 5244 个蛋白编码基因和一个整合性接合元件区域，包含 79 个 ORF 序列。AHKv-S01 被赋予了新的序列类型 174。系统发育分析表明，rpoB 部分核苷酸序列高度可靠，可用于鉴定阿克沙基氏菌属。AHKv-S01 的 340 个特有基因主要参与细胞包膜生物发生、转录、运输和代谢过程。此外，AHKv-S01 对多种抗生素敏感，但对青霉素、大环内酯类和林可酰胺类具有很强的耐药性。基因组包含三个药物外排泵超家族、β-内酰胺酶基因和磷霉素耐药相关基因。大多数耐药基因显示氨基酸突变。还鉴定了多种毒力和致病因子，主要与粘附、分泌、铁获取和免疫逃避有关。鸡胚致死性试验结果表明，AHKv-S01、肺炎克雷伯菌 ATCC10031 和肺炎克雷伯菌 CICC24714 的 7 日龄鸡胚致死率分别为 80%、40%和 50%。AHKv-S01 的半数致死剂量为 39.9 CFU/胚。即使低水平感染 AHKv-S01 也会导致鸡胚孵化率显著降低。感染 AHKv-S01 的胚胎肝脏、心脏和脑组织出现严重病变，且心脏和脑组织的病变早于肝脏。总之，本研究结果为进一步评估阿克沙基氏菌对家禽种群和生产产量的潜在风险提供了基础。
