Abstract：
Lytic bacteriophages are promising biocontrol agents against pathogenic bacteria for food and therapeutic applications. Investigating the feasibility of combining phage and physical lethal agents, such as heat, as an effective hurdle combination could lead to beneficial applications. The current research was initiated to compare the thermal inactivation kinetics of a lytic phage (Escherichia phage OSYSP) and its host (Shiga toxin-producing Escherichia coli O157:H7 EDL933), considering they have different critical thermal targets in their structures. To provide a basis for comparison, thermal inactivation kinetics were determined on suspensions of these agents in buffered peptone water using a thermally controlled circulating water bath. Results showed that the bacteriophage virions have a remarkable heat resistance (p < 0.05) compared to their host cells. The D-values of the populations of phage (PFU/mL) and EDL933 strain (CFU/mL) were 166.7 and 7.3 min at 55°C, compared to 44.4 and 0.3 min at 60°C, respectively. Additionally, D-values were significantly (p < 0.05) more influenced by temperature changes in the case of E. coli O157:H7 EDL933 (z-value 3.7°C) compared to that for phage OSYSP (z-value 7.7°C). When the phage suspension was heat-treated in a thermal cycler instead of a water bath, no significant differences between the two treatment procedures (p > 0.05) in estimating virus D- and z-values were observed. Based on these findings, it may be feasible to combine phage OSYSP with mild heat during processing of food to selectively inactivate E. coli O157:H7 EDL933 and subsequently maintain product safety during storage by the surviving phage population; however, the feasibility of this application needs to be investigated. Additionally, the relatively heat-resistant phage OSYSP could qualify as a biological indicator to validate thermal treatments of minimally processed foods in which E. coli O157:H7 EDL933 is the pathogen-of-concern.
摘要：
裂解噬菌体是用于食品和治疗应用的有前途的针对病原菌的生物防治剂。研究结合噬菌体和物理致死剂的可行性，比如热，作为有效的障碍组合可以带来有益的应用。当前的研究是为了比较裂解噬菌体（大肠杆菌噬菌体OSYSP）及其宿主（产生志贺毒素的大肠杆菌O157：H7EDL933）的热失活动力学，考虑到他们的结构有不同的临界热目标。为比较提供依据,使用热控制循环水浴确定这些试剂在缓冲蛋白胨水中的悬浮液的热失活动力学。结果表明,噬菌体病毒粒子与其宿主细胞相比具有显著的耐热性(p<0.05)。在55°C下，噬菌体（PFU/mL）和EDL933菌株（CFU/mL）种群的D值分别为166.7和7.3分钟，与60°C时的44.4和0.3分钟相比，分别。此外,与噬菌体OSYSP(z值7.7°C)相比,在大肠杆菌O157:H7EDL933(z值3.7°C)的情况下,D值显著(p<0.05)更受温度变化的影响。当噬菌体悬浮液在热循环仪而不是水浴中热处理时，在估计病毒D值和z值方面,两种治疗程序之间没有观察到显著差异(p>0.05)。基于这些发现,在食品加工过程中，将噬菌体OSYSP与温和的热量结合起来，以选择性灭活大肠杆菌O157:H7EDL933，并随后在存活的噬菌体种群的储存过程中保持产品安全是可行的；然而，这种应用的可行性有待研究。此外,相对耐热的噬菌体OSYSP可以作为生物学指标来验证最低限度加工食品的热处理,其中大肠杆菌O157:H7EDL933是关注的病原体.
