Levine Uri Y, Bearson Shawn M D, Stanton Thad B
Food Safety and Enteric Pathogens Research Unit, National Animal Disease Center, Agricultural Research Service, United States Department of Agriculture, Ames, IA 50010, USA.
Vet Microbiol. 2012 Sep 14;159(1-2):115-22. doi: 10.1016/j.vetmic.2012.03.027. Epub 2012 Mar 27.
Salmonella continues to be a significant human health threat, and the objective of this study was to identify microorganisms with the potential to improve porcine food-safety through their antagonism of Salmonella. Anaerobic culture supernatants of 973 bacterial isolates from the gastrointestinal tract and feces of swine were screened for their capacity to inhibit the growth of Salmonella enterica serovar Typhimurium. Growth inhibition of 1000-fold or greater was observed from 16 isolates, and 16S rRNA sequencing identified the isolates as members of the genera Mitsuokella, Escherichia/Shigella, Anaerovibrio, Selenomonas, and Streptococcus. Four isolates were identified as Mitsuokella jalaludinii, and the mechanism of Salmonella Typhimurium growth inhibition by M. jalaludinii was further investigated. M. jalaludinii stationary phase culture supernatants were observed to significantly inhibit growth, and featured the production of lactic, succinic, and acetic acids. Aerobic and anaerobic S. Typhimurium growth was restored when the pH of the culture supernatants (pH 4.6) was increased to pH 6.8. However, S. Typhimurium growth in fermentation acid-free media was the same at pH 4.6 and pH 6.8 - indicating a synergistic effect between fermentation acid production and low pH as the cause of S. Typhimurium growth inhibition. Furthermore, exposure of S. Typhimurium to M. jalaludinii culture supernatants inhibited Salmonella invasion of HEp-2 cells by 10-fold. The results identify M. jalaludinii as a possible inhibitor of Salmonella growth and invasion in swine, and thus a potential probiotic capable of improving food safety.
沙门氏菌仍然是对人类健康的重大威胁，本研究的目的是鉴定具有通过拮抗沙门氏菌来改善猪食品安全潜力的微生物。对来自猪胃肠道和粪便的973株细菌分离株的厌氧培养上清液进行筛选，以检测其抑制鼠伤寒沙门氏菌生长的能力。从16株分离株中观察到了1000倍或更高倍数的生长抑制，16S rRNA测序确定这些分离株为 Mitsuokella、大肠杆菌/志贺氏菌属、厌氧弧菌属、月形单胞菌属和链球菌属的成员。有4株分离株被鉴定为贾氏 Mitsuokella，进一步研究了贾氏 Mitsuokella抑制鼠伤寒沙门氏菌生长的机制。观察到贾氏 Mitsuokella 稳定期培养上清液能显著抑制生长，且其特征在于产生乳酸、琥珀酸和乙酸。当培养上清液的pH值（pH 4.6）提高到pH 6.8时，需氧和厌氧条件下的鼠伤寒沙门氏菌生长得以恢复。然而，在无发酵酸的培养基中，鼠伤寒沙门氏菌在pH 4.6和pH 6.8时的生长情况相同，这表明发酵酸产生和低pH之间存在协同作用，是抑制鼠伤寒沙门氏菌生长的原因。此外，将鼠伤寒沙门氏菌暴露于贾氏 Mitsuokella 培养上清液中可使沙门氏菌对HEp-2细胞的侵袭能力降低10倍。这些结果确定贾氏 Mitsuokella 可能是猪体内沙门氏菌生长和侵袭的抑制剂，因此是一种有潜力改善食品安全的益生菌。
