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Abstract：
Background Salmonella enterica is a significant foodborne pathogen that causes considerable illness and death in humans and animals. The clustered regularly interspaced short palindromic repeat (CRISPR)-CRISPR-associated protein (Cas) system in bacteria acts as an adaptive immune defense against invasive genetic elements by incorporating short intergenic spacers (IGSs) into CRISPR loci. These loci serve as molecular records of past interactions with phages and plasmids, providing insights into the transmission and evolution of bacterial strains across different hosts. Aim This study aimed to investigate the diversity of IGSs in the CRISPR-1 locus of S. enterica isolates from humans and camels. The objective was to assess the potential of IGSs to distinguish strains, track sources, and understand patterns of zoonotic transmission. Materials and methods Genomic DNA was extracted from multiple strains of S. enterica, and the CRISPR-1 locus was polymerase chain reaction (PCR) amplified and sequenced. The sequences were compared to identify distinct patterns of IGSs and potential host-specific characteristics. Sanger sequencing and bioinformatics tools were used to classify the IGSs and determine their similarity to known sequences in the National Center for Biotechnology Information (NCBI) database. Results Sequence analysis revealed five distinct CRISPR-1 types among S. enterica isolates from humans and three among camel isolates. The presence of shared IGSs between human and camel S. enterica isolates suggested zoonotic or reverse-zoonotic transmission events. Additionally, host-specific unknown IGSs (UIGS) were identified. Importantly, camel isolates initially identified as S. enterica subspecies enterica serovar Enteritidis based on rrnH gene sequencing were reclassified as S. enterica serovar Enteritidis based on CRISPR-1 profiling, demonstrating the higher resolution of CRISPR-based genotyping. Conclusion The diversity of IGSs in the CRISPR-1 locus effectively differentiated S. enterica strains and provided insights into their evolutionary origins and transmission dynamics. CRISPR-based genotyping proves to be a promising tool to complement traditional serotyping methods, enhancing the molecular epidemiology of salmonellosis and potentially leading to better management and control strategies for this pathogen.
摘要：
背景技术肠沙门氏菌是一种重要的食源性病原体,在人类和动物中引起相当大的疾病和死亡。细菌中成簇的规则间隔短回文重复序列（CRISPR）-CRISPR相关蛋白（Cas）系统通过将短的基因间间隔区（IGSs）整合到CRISPR基因座中来充当针对侵入性遗传因素的适应性免疫防御。这些基因座是过去与噬菌体和质粒相互作用的分子记录，提供对细菌菌株在不同宿主之间的传播和进化的见解。目的本研究旨在研究人类和骆驼肠球菌分离株CRISPR-1位点IGSs的多样性。目的是评估IGSs区分菌株的潜力，跟踪源，了解人畜共患传播的模式。材料和方法从多个肠球菌菌株中提取基因组DNA，并对CRISPR-1位点进行聚合酶链反应(PCR)扩增和测序。比较序列以鉴定IGS的不同模式和潜在的宿主特异性特征。使用Sanger测序和生物信息学工具对IGS进行分类，并确定其与国家生物技术信息中心（NCBI）数据库中已知序列的相似性。结果序列分析揭示了人类肠球菌分离株中的五种不同的CRISPR-1类型，骆驼分离株中的三种。人与骆驼肠球菌分离株之间存在共有IGS，提示人畜共患或反向人畜共患传播事件。此外,确定了宿主特异性未知IGS（UIGS）。重要的是,根据rrnH基因测序最初鉴定为肠道链球菌亚种肠道血清型肠炎的骆驼分离株根据CRISPR-1谱重新分类为肠道链球菌。证明了基于CRISPR的基因分型的分辨率更高。结论CRISPR-1位点IGSs的多样性有效地分化了肠球菌菌株，并为其进化起源和传播动态提供了见解。基于CRISPR的基因分型被证明是补充传统血清分型方法的有希望的工具，加强沙门氏菌病的分子流行病学，并可能导致更好的管理和控制策略。
