Induction of a Viable but Nonculturable State, Thermal and Sanitizer Tolerance, and Gene Expression Correlation with Desiccation-Adapted Biofilm and Planktonic Salmonella in Powdered Infant Formula
Induction of a Viable but Nonculturable State, Thermal and Sanitizer Tolerance, and Gene Expression Correlation with Desiccation-Adapted Biofilm and Planktonic Salmonella in Powdered Infant Formula
复制标题
DOI：
10.4315/jfp-20-402
复制
发表时间：
2021-07-01
影响因子：
2
通讯作者：
Zhang, Hongmei
中科院分区：
文献类型：
--
作者：
Chen, Guiliu;Lin, Mengzhe;Zhang, Hongmei
本研究旨在探讨婴幼儿配方奶粉的生理状态、干燥适应和储存对沙门氏菌细胞存活和干燥应激相关基因表达的影响。将婴儿配方奶粉接种鼠伤寒沙门氏菌，在珠子上以生物膜状态接种，并在硝酸纤维素过滤器上以浮游状态接种，并在25摄氏度下储存长达270天。流式细胞术和木糖赖氨酸脱氧胆酸琼脂平板计数均显示形成生物膜的沙门氏菌细胞倾向于进入活的但不可培养(VBNC)状态(P<；0.05)。在温和的高温(60摄氏度)下，所有干燥适应的鼠伤寒沙门氏菌在两种生理状态下的种群减少都显著低于非适应的对照细胞(P<；0.05)。沙门氏菌细胞在两种生理状态下都受到交叉保护，但对过氧化氢的交叉保护只对浮游沙门氏菌细胞产生。逆转录定量聚合酶链式反应结果显示，所有干燥适应日的生物膜沙门氏菌细胞和干燥储存第7天的浮游沙门氏菌细胞中的rpos基因均显著上调(P<；0.05)。在两种生理状态下，沙门氏菌细胞的rpoE、GRPE和invA基因均显著下调(P<；0.05)。生理状态和贮藏时间可能会影响这些基因的表达。高生物膜沙门氏菌比浮游沙门氏菌更容易进入VBNC状态。干燥适应的生物膜和浮游沙门氏菌细胞诱导热交叉保护。浮游细胞的干旱适应可以诱导对过氧化氢的交叉保护。rpos基因在干燥胁迫条件下可能起关键作用。
This study was conducted to investigate the effects of the physiological state, desiccation adaptation, and storage of powdered infant formula on Salmonella cell survival and expression of desiccation stress-related genes. Powdered infant formula was inoculated with Salmonella Typhimurium in the biofilm state on beads and in the planktonic state on nitrocellulose filters and stored at 25 degrees C for up to 270 days. Both 5-cyano-2,3-ditoyl tetrazolium chloride flow cytometry and xylose lysine deoxycholate agar plate counts revealed that biofilm-forming Salmonella cells tended to enter the viable but nonculturable (VBNC) state (P < 0.05). The population reduction of all desiccation-adapted Salmonella Typhimurium decreased significantly in both physiological states after exposure to mild heat (60 degrees C) compared with nonadapted control cells (P < 0.05). Salmonella cells were cross-protected from heat in both physiological states, but cross-protection against hydrogen peroxide was induced for only planktonic Salmonella cells. The reverse transcription quantitative PCR results revealed that the rpoS gene in biofilm Salmonella cells on all desiccation adaption days and in planktonic Salmonella cells on day 7 of dry storage was significantly upregulated (P < 0.05). The rpoE, grpE, and invA genes in Salmonella cells in both physiological states were significantly down-regulated (P < 0.05). Physiological state and storage time might affect expression of these genes. Prior exposure to adverse conditions, including low water activity, and the physiological state impacted Salmonella survival, and its ability to enter the VBNC state and gene expression.HIGHLIGHTSBiofilm Salmonella cells were more likely to enter the VBNC state than were planktonic cells.Heat cross-protection was induced in dry-adapted biofilm and planktonic Salmonella cells.Dry adaptation in planktonic cells can induce cross-protection against hydrogen peroxide.The rpoS gene may play a crucial role under desiccation stress conditions.