Department of Microbiology, Faculty of Science, Lagos State University, Ojo, Lagos, Nigeria.
Institute of Bacterial Infections and Zoonoses, Friedrich-Loeffler-Institute, Jena, Germany.
BMC Microbiol. 2023 Jun 13;23(1):164. doi: 10.1186/s12866-023-02901-1.
Salmonella infections remain an important public health issue worldwide. Some serovars of non-typhoidal Salmonella (NTS) have been associated with bloodstream infections and gastroenteritis, especially in children in Sub-Saharan Africa with circulating S. enterica serovars with drug resistance and virulence genes. This study identified and verified the clonal relationship of Nigerian NTS strains isolated from humans, animals, and the environment.
In total, 2,522 samples were collected from patients, animals (cattle and poultry), and environmental sources between December 2017 and May 2019. The samples were subjected to a standard microbiological investigation. All the isolates were identified using Microbact 24E, and MALDI-TOF MS. The isolates were serotyped using the Kauffmann-White scheme. Antibiotic susceptibility testing was conducted using the disc diffusion method and the Vitek 2 compact system. Virulence and antimicrobial resistance genes, sequence type, and cluster analysis were investigated using WGS data.
Forty-eight (48) NTS isolates (1.9%) were obtained. The prevalence of NTS from clinical sources was 0.9%, while 4% was recorded for animal sources. The serovars identified were S. Cotham (n = 17), S. Give (n = 16), S. Mokola (n = 6), S. Abony (n = 4), S. Typhimurium (n = 4), and S. Senftenberg (n = 1). All 48 Salmonella isolates carried intrinsic and acquired resistant genes such as aac.6…Iaa, mdf(A), qnrB, qnrB19 genes and golT, golS, pcoA, and silP, mediated by plasmid Col440I_1, incFIB.B and incFII. Between 100 and 118 virulence gene markers distributed across several Salmonella pathogenicity islands (SPIs), clusters, prophages, and plasmid operons were found in each isolate. WGS revealed that strains of each Salmonella serovar could be assigned to a single 7-gene MLST cluster, and strains within the clusters were identical strains and closely related as defined by the 0 and 10 cgSNPs and likely shared a common ancestor. The dominant sequence types were S. Give ST516 and S. Cotham ST617.
We found identical Salmonella sequence types in human, animal, and environmental samples in the same locality, which demonstrates the great potential of the applied tools to trace back outbreak strains. Strategies to control and prevent the spread of NTS in the context of one's health are essential to prevent possible outbreaks.
沙门氏菌感染仍是全球重要的公共卫生问题。一些非伤寒沙门氏菌（NTS）血清型与血流感染和肠胃炎有关，尤其是在撒哈拉以南非洲地区，循环的 S. enterica 血清型具有耐药性和毒力基因。本研究鉴定并验证了从人类、动物和环境中分离出的尼日利亚 NTS 菌株的克隆关系。
2017 年 12 月至 2019 年 5 月期间，共从患者、动物（牛和家禽）和环境源采集了 2522 份样本。样本进行了标准微生物学调查。所有分离株均使用 Microbact 24E 和 MALDI-TOF MS 进行鉴定。使用 Kauffmann-White 方案对分离株进行血清分型。使用纸片扩散法和 Vitek 2 紧凑型系统进行抗生素敏感性试验。使用 WGS 数据研究毒力和抗菌药物耐药基因、序列类型和聚类分析。
共获得 48 株（48%）NTS 分离株。临床来源的 NTS 患病率为 0.9%，而动物来源的 NTS 患病率为 4%。鉴定的血清型为 S. Cotham（n=17）、S. Give（n=16）、S. Mokola（n=6）、S. Abony（n=4）、S. Typhimurium（n=4）和 S. Senftenberg（n=1）。所有 48 株沙门氏菌分离株均携带内在和获得性耐药基因，如 aac.6Ⅰaa、mdf(A)、qnrB、qnrB19 基因和 golT、golS、pcoA 和 silP，由质粒 Col440I_1、incFIB.B 和 incFII 介导。在每个分离株中发现了分布在多个沙门氏菌致病性岛（SPIs）、聚类、噬菌体和质粒操纵子中的 100 至 118 个毒力基因标记。WGS 显示，每种血清型的菌株都可以分配到一个单一的 7 基因 MLST 聚类中，聚类内的菌株是相同的菌株，并且根据 0 和 10 cgSNPs 定义的密切相关，可能具有共同的祖先。主要的序列类型是 S. Give ST516 和 S. Cotham ST617。
我们在同一地点的人类、动物和环境样本中发现了相同的沙门氏菌序列类型，这表明所应用的工具具有追溯暴发菌株的巨大潜力。控制和预防 NTS 在卫生方面传播的策略对于预防可能的暴发至关重要。
