Antimicrobial Susceptibility Testing Result.

Salmonella, a significant threat to public safety, inflicts substantial economic losses on the poultry industry. The unique “parental feeding” breeding model of pigeon farms, against the “all-in & all-out” biosecurity strategy, makes them susceptible to Salmonella infections and subsequent outbreaks of pigeon paratyphoid. This study initially studied three pigeon paratyphoid outbreak incidents in Henan, China, in which 53 strains of pigeon-origin Salmonella Typhimurium (STM) were identified. Whole-genome sequencing (WGS) and antimicrobial-resistant profile analysis revealed that the three outbreaks were caused by distinct STM clones (ST128-DT2, ST19-DT99). Global phylogenetic analysis suggested that the United States is a possible origin, indicating a risk of intercontinental transmission via pigeon eggs. Further bacterial virulence and invasion assays, including in vitro and in vivo assays, revealed that pigeon-host-adaptive STM, compared to broad-host-range STM, carried fewer resistance genes, exhibited higher invasion indices and pseudogene levels, displayed a non-rdar (red dry and rough) phenotype, and had strong biofilm formation capability. Additionally, they showed reduced virulence and invasiveness in mice but a pigeon-adaptive feature in cogent models. The collective results support the host adaptation for pigeons among DT2 and DT99 phage-type isolates.沙门氏菌（Salmonella）是威胁公共安全的重大隐患，同时给家禽养殖业造成了巨额经济损失。鸽场独特的“亲代哺育”养殖模式与“全进全出”生物安全防控策略相悖，使得鸽群极易感染沙门氏菌，进而暴发鸽副伤寒。本研究针对中国河南省的三起鸽副伤寒暴发事件展开调查，共分离鉴定出53株鸽源鼠伤寒沙门氏菌（Salmonella Typhimurium, STM）。通过全基因组测序（Whole-genome sequencing, WGS）与耐药谱分析，发现这三起暴发事件分别由不同的STM克隆株（ST128-DT2、ST19-DT99）引发。全球系统发育分析显示，该病原菌可能起源于美国，提示存在通过鸽蛋进行跨洲际传播的风险。后续开展的细菌毒力与侵袭力实验（涵盖体外与体内实验）结果表明，相较于广谱宿主范围的沙门氏菌，鸽源适应性STM的耐药基因携带量更少，侵袭指数与假基因水平更高，呈现非rdar（红色干燥粗糙）表型，且具备较强的生物膜形成能力。此外，该类菌株在小鼠模型中毒力与侵袭性有所降低，但在鸽源实验模型中则展现出鸽适应性特征。综合以上研究结果，证实DT2与DT99噬菌体型分离株具备鸽宿主适应性。