Clemente-Carazo Marta, Leal José-Juan, Huertas Juan-Pablo, Garre Alberto, Palop Alfredo, Periago Paula M
Departamento Ingeniería Agronómica, Campus de Excelencia Internacional Regional "Campus Mare Nostrum", Instituto de Biotecnología Vegetal, Escuela Técnica Superior de Ingeniería Agronómica, Universidad Politécnica de Cartagena, Cartagena, Spain.
Food Microbiology, Wageningen University & Research, Wageningen, Netherlands.
Front Microbiol. 2021 Sep 20;12:691248. doi: 10.3389/fmicb.2021.691248. eCollection 2021.
Microbial cells respond to sub-lethal stresses with several physiological changes to increase their chance of survival. These changes are of high relevance when combined treatments (hurdle technology) are applied during food production, as the cells surviving the first hurdle may have greater resistance to subsequent treatments than untreated cells. In this study, we analyzed if develops increased resistance to thermal treatments after the application of an acid shock. We compared the heat resistance of acid-shocked (pH 4.5 achieved with citric acid) cells with that of cells maintained at pH 7 (control cells). Thermal treatments were performed between 57.5 and 65°C. We observed a differential response between the two strains studied. Acid-shocked cells of Senftenberg exhibited reduced heat resistance, e.g., for a treatment at 60.0°C and pH 7.0 the time required to reduce the population by 3 log cycles was lowered from 10.75 to 1.98min with respect to control cells. Enteritidis showed a different response, with acid-shocked cells having similar resistance than untreated cells (the time required to reduce 3 log cycles at 60.0°C and pH 7.0 was 0.30min for control and 0.31min for acid-shock cells). Based on results by differential plating (with or without adding the maximum non-inhibitory concentration of NaCl to the recovery medium), we hypothesize that the differential response between strains can be associated to sub-lethal damage to the cell membrane of . Senftenberg caused by the acid shock. These results provide evidence that different strains of the same species can respond differently to an acid shock and highlight the relevance of cross-resistances for microbial risk assessment.
微生物细胞会通过多种生理变化来应对亚致死应激，以增加其存活几率。当在食品生产过程中应用联合处理（栅栏技术）时，这些变化具有高度相关性，因为在第一道栅栏中存活下来的细胞可能比未处理的细胞对后续处理具有更强的抵抗力。在本研究中，我们分析了在施加酸冲击后，[具体菌株名称]是否会对热处理产生更高的抗性。我们将经酸冲击处理（用柠檬酸将pH值调至4.5）的细胞与维持在pH 7的细胞（对照细胞）的耐热性进行了比较。热处理在57.5至65°C之间进行。我们观察到所研究的两种菌株之间存在差异反应。森弗滕贝格[具体菌株名称]经酸冲击处理的细胞耐热性降低，例如，在60.0°C和pH 7.0条件下处理时，相对于对照细胞，使菌数减少3个对数循环所需的时间从10.75分钟降至1.98分钟。肠炎沙门氏菌表现出不同的反应，经酸冲击处理的细胞与未处理的细胞具有相似的抗性（在60.0°C和pH 7.0条件下使菌数减少3个对数循环所需的时间，对照细胞为0.30分钟，酸冲击处理的细胞为0.31分钟）。基于差异平板计数结果（在复苏培养基中添加或不添加最大非抑制浓度的氯化钠），我们推测菌株之间的差异反应可能与酸冲击对森弗滕贝格[具体菌株名称]细胞膜造成的亚致死损伤有关。这些结果提供了证据，表明同一物种的不同菌株对酸冲击的反应可能不同，并突出了交叉抗性在微生物风险评估中的相关性。
