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Abstract：
BACKGROUND: Salmonella, an important foodborne pathogen, was estimated to be responsible for 95.1 million cases and 50,771 deaths worldwide. Sixteen serovars were responsible for approximately 80% of Salmonella infections in humans in China, and infections caused by a few uncommon serovars have been reported in recent years, though not with S. Welikade. This study reports the first clinical case caused by S. Welikade in China and places Chinese S. Welikade isolates in the context of global isolates via genomic analysis. For comparison, S. Welikade isolates were also screened in the Chinese Local Surveillance System for Salmonella (CLSSS). The minimum inhibitory concentrations (MICs) of 28 antimicrobial agents were determined using the broth microdilution method. The isolates were sequenced on an Illumina platform to identify antimicrobial resistance genes, virulence genes, and phylogenetic relationships.
RESULTS: The S. Welikade isolate (Sal097) was isolated from a two-year-old boy with acute gastroenteritis in 2021. Along with the other two isolates found in CLSSS, the three Chinese isolates were susceptible to all the examined antimicrobial agents, and their sequence types (STs) were ST5123 (n = 2) and ST3774 (n = 1). Single nucleotide polymorphism (SNP)-based phylogenetic analysis revealed that global S. Welikade strains can be divided into four groups, and these three Chinese isolates were assigned to B (n = 2; Sal097 and XXB1016) and C (n = 1; XXB700). In Group B, the two Chinese ST5123 isolates were closely clustered with three UK ST5123 isolates. In Group C, the Chinese isolate was closely related to the other 12 ST3774 isolates. The number of virulence genes in the S. Welikade isolates ranged from 59 to 152. The galF gene was only present in Group A, the pipB2 gene was only absent from Group A, the avrA gene was only absent from Group B, and the allB, sseK1, sspH2, STM0287, and tlde1 were found only within Group C and D isolates. There were 15 loci unique to the Sal097 isolate.
CONCLUSIONS: This study is the first to characterize and investigate clinical S. Welikade isolates in China. Responsible for a pediatric case of gastroenteritis in 2021, the clinical isolate harbored no antimicrobial resistance and belonged to phylogenetic Group B of global S. Welikade genomes.
RESULTS: The S. Welikade isolate (Sal097) was isolated from a two-year-old boy with acute gastroenteritis in 2021. Along with the other two isolates found in CLSSS, the three Chinese isolates were susceptible to all the examined antimicrobial agents, and their sequence types (STs) were ST5123 (n = 2) and ST3774 (n = 1). Single nucleotide polymorphism (SNP)-based phylogenetic analysis revealed that global S. Welikade strains can be divided into four groups, and these three Chinese isolates were assigned to B (n = 2; Sal097 and XXB1016) and C (n = 1; XXB700). In Group B, the two Chinese ST5123 isolates were closely clustered with three UK ST5123 isolates. In Group C, the Chinese isolate was closely related to the other 12 ST3774 isolates. The number of virulence genes in the S. Welikade isolates ranged from 59 to 152. The galF gene was only present in Group A, the pipB2 gene was only absent from Group A, the avrA gene was only absent from Group B, and the allB, sseK1, sspH2, STM0287, and tlde1 were found only within Group C and D isolates. There were 15 loci unique to the Sal097 isolate.
CONCLUSIONS: This study is the first to characterize and investigate clinical S. Welikade isolates in China. Responsible for a pediatric case of gastroenteritis in 2021, the clinical isolate harbored no antimicrobial resistance and belonged to phylogenetic Group B of global S. Welikade genomes.
摘要：
背景：沙门氏菌，一种重要的食源性病原体，据估计，全球有9510万例病例和50,771例死亡。在中国，约有80%的人感染沙门氏菌，近年来报道了一些不常见的血清型引起的感染，虽然不是S.Welikade.本研究报告了中国首例由S.Welikade引起的临床病例，并通过基因组分析将中国S.Welikade分离株置于全球分离株的背景下。为了比较，还在中国沙门氏菌本地监测系统（CLSSS）中筛选了S.Welikade分离株。使用肉汤微量稀释法确定28种抗菌剂的最小抑制浓度（MIC）。在Illumina平台上对分离株进行测序，以鉴定抗微生物药物抗性基因，毒力基因，和系统发育关系。
结果：S.Welikade分离株（Sal097）于2021年从一名患有急性胃肠炎的2岁男孩中分离出来。连同在CLSSS中发现的另外两个分离株，这三个中国分离株对所有被检查的抗菌药物都敏感，其序列类型为ST5123(n=2)和ST3774(n=1)。基于单核苷酸多态性（SNP）的系统发育分析表明，全球S.Welikade菌株可分为四组，将这三个中国分离株分为B（n=2；Sal097和XXB1016）和C（n=1；XXB700）。B组,两个中国ST5123分离株与三个英国ST5123分离株紧密聚集。C组,中国分离株与其他12个ST3774分离株密切相关。S.Welikade分离株中的毒力基因的数量范围为59至152。galF基因只存在于A组中,pipB2基因仅在A组中缺失，avrA基因只在B组中缺失,和所有的B，sseK1，sspH2，STM0287和tlde1仅在C和D组分离株中发现。Sal097分离株有15个独特的基因座。
结论：本研究首次对中国的临床S.Welikade分离株进行表征和调查。该临床分离株负责2021年的小儿胃肠炎病例，不具有抗菌素耐药性，属于全球S.Welikade基因组的系统发育组B。
结果：S.Welikade分离株（Sal097）于2021年从一名患有急性胃肠炎的2岁男孩中分离出来。连同在CLSSS中发现的另外两个分离株，这三个中国分离株对所有被检查的抗菌药物都敏感，其序列类型为ST5123(n=2)和ST3774(n=1)。基于单核苷酸多态性（SNP）的系统发育分析表明，全球S.Welikade菌株可分为四组，将这三个中国分离株分为B（n=2；Sal097和XXB1016）和C（n=1；XXB700）。B组,两个中国ST5123分离株与三个英国ST5123分离株紧密聚集。C组,中国分离株与其他12个ST3774分离株密切相关。S.Welikade分离株中的毒力基因的数量范围为59至152。galF基因只存在于A组中,pipB2基因仅在A组中缺失，avrA基因只在B组中缺失,和所有的B，sseK1，sspH2，STM0287和tlde1仅在C和D组分离株中发现。Sal097分离株有15个独特的基因座。
结论：本研究首次对中国的临床S.Welikade分离株进行表征和调查。该临床分离株负责2021年的小儿胃肠炎病例，不具有抗菌素耐药性，属于全球S.Welikade基因组的系统发育组B。
