Veni Krishna, Stephen Jerusha, Lekshmi Manjusha, Nayak Binaya Bhusan, Kumar Sanath H
ICAR-Central Institute of Fisheries Education, Quality Control Laboratory, Fish Processing Technology Department, Mumbai 400061, India.
J AOAC Int. 2025 Jan 1;108(1):56-61. doi: 10.1093/jaoacint/qsae081.
Salmonella Infantis is an emerging multidrug-resistant pathogen worldwide due to the acquisition of a megaplasmid, plasmid of emerging Salmonella Infantis (pESI). Reported initially in poultry, the distribution of pESI-harboring S. Infantis in other food types, including seafood, is unknown.
This study aimed to develop and optimize a PCR assay for detecting the pESI in Salmonella and non-Salmonella Enterobacterales.
A duplex PCR targeting the hilA gene and a pESI-associated gene of S. Infantis was designed, and the PCR conditions were optimized. The specificity and sensitivity of the assay were established using 119 Salmonella serovars and 51 non-Salmonella bacterial strains.
All Salmonella isolates yielded hilA PCR product, while only pESI S. Infantis was positive for both hilA and pESI genes. No amplification product was obtained with the DNA of 51 non-Salmonella bacterial strains. The detection limit of the duplex PCR was 104 CFU/mL of pure culture of pESI S. Infantis. The sensitivity of detection in artificially spiked shrimp meat was 1 CFU/g after 6 h of enrichment in lactose broth, followed by 12 h of selective enrichment in the Rappaport-Vassiliadis medium.
The duplex assay will help screen seafood for Salmonella in general and pESI S. Infantis in particular. Given its high sensitivity, the PCR will be a valuable tool for seafood quality assurance. This approach decreases the typical 3-6 day identification time of Salmonella to less than 24 h.
S. Infantis carrying the highly transmissible megaplasmid (pESI) is a significant food safety concern. Given its rapid geographical spread and high antimicrobial-resistant traits, it is necessary to have a molecular tool that detects pESI-harboring Salmonella. This study successfully developed a duplex PCR assay that simultaneously detects Salmonella enterica and pESI S. Infantis. This molecular tool will help understand the distribution, sources, and spread of the multidrug-resistance (MDR) plasmid in the food environment.
婴儿沙门氏菌是一种在全球范围内新出现的多重耐药病原体，因为它获得了一个大质粒，即新出现的婴儿沙门氏菌质粒（pESI）。该菌最初在家禽中被报道，而携带pESI的婴儿沙门氏菌在包括海鲜在内的其他食物类型中的分布情况尚不清楚。
本研究旨在开发并优化一种用于检测沙门氏菌和非沙门氏菌肠杆菌科细菌中pESI的PCR检测方法。
设计了一种针对婴儿沙门氏菌hilA基因和一个与pESI相关基因的双重PCR，并对PCR条件进行了优化。使用119种沙门氏菌血清型和51种非沙门氏菌菌株确定了该检测方法的特异性和灵敏度。
所有沙门氏菌分离株均产生hilA PCR产物，而只有携带pESI的婴儿沙门氏菌的hilA和pESI基因均为阳性。51种非沙门氏菌菌株的DNA未获得扩增产物。双重PCR的检测限为携带pESI的婴儿沙门氏菌纯培养物104 CFU/mL。在乳糖肉汤中富集6小时，然后在Rappaport-Vassiliadis培养基中进行12小时选择性富集后，在人工接种虾肉中的检测灵敏度为1 CFU/g。
这种双重检测方法将有助于一般地筛查海鲜中的沙门氏菌，特别是携带pESI的婴儿沙门氏菌。鉴于其高灵敏度，该PCR将成为海鲜质量保证的有价值工具。这种方法将沙门氏菌通常3至6天的鉴定时间缩短至不到24小时。
携带高度可传播大质粒（pESI）的婴儿沙门氏菌是一个重大的食品安全问题。鉴于其迅速的地理传播和高耐药特性，有必要拥有一种检测携带pESI的沙门氏菌的分子工具。本研究成功开发了一种双重PCR检测方法，可同时检测肠炎沙门氏菌和携带pESI的婴儿沙门氏菌。这种分子工具将有助于了解多重耐药（MDR）质粒在食品环境中的分布、来源和传播。
