Mangieri Nicola, Vieira Rui P, Picozzi Claudia
DeFENS, Department of Food, Environmental and Nutritional Sciences, Università Degli Studi di Milano, Milano, Italy.
Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal.
Front Microbiol. 2023 Sep 28;14:1270346. doi: 10.3389/fmicb.2023.1270346. eCollection 2023.
Shiga toxin-producing (STEC) are foodborne pathogens implicated in diseases including hemolytic uremic syndrome (HUS) and hemorrhagic colitis (HC). The main virulence factor are Shiga toxins; their production and secretion are by-products of the expression of late genes of prophages upon sub-lethal environmental stimuli exposure. Hence, the lysogenic prophage after a stress switch to lytic cycle spreading the Stx phages. In the present study, 35 STEC were screened for the presence and the ability to release Shiga toxin-encoding bacteriophages. Three bacterial strains showed signals of prophage presence both in plate and in PCR. Subsequently, these bacterial strains were subjected to stressors that simulate cheese manufacturing conditions: NaCl (1, 1.5 and 2% w/v), lactic acid (0.5, 1.5 and 3% v/v), anaerobic growth, pasteurization (72°C for 15 s), UV irradiation. The ability to release prophage was evaluated by Real Time qPCR. Induction of the prophages showed that the addition of NaCl at 1.5 and 2% significantly increased viral release compared to control. Conversely, the addition of lactic acid had a significant repressive effect. The other applied stressors had no significant effect in phage release according to the experimental conditions adopted.
产志贺毒素大肠杆菌（STEC）是食源性病原体，可引发包括溶血性尿毒症综合征（HUS）和出血性结肠炎（HC）在内的疾病。其主要毒力因子是志贺毒素；毒素的产生和分泌是前噬菌体晚期基因在亚致死环境刺激下表达的副产物。因此，溶原性前噬菌体在应激后切换到裂解周期，从而传播stx噬菌体。在本研究中，对35株STEC进行了志贺毒素编码噬菌体存在情况及释放能力的筛选。三株细菌菌株在平板和PCR检测中均显示出前噬菌体存在的信号。随后，对这些细菌菌株施加模拟奶酪制造条件的应激源：NaCl（1%、1.5%和2% w/v）、乳酸（0.5%、1.5%和3% v/v）、厌氧生长、巴氏杀菌（72°C处理15秒）、紫外线照射。通过实时定量PCR评估前噬菌体的释放能力。前噬菌体的诱导结果表明，与对照相比，添加1.5%和2%的NaCl显著增加了病毒释放。相反，添加乳酸具有显著的抑制作用。根据所采用的实验条件，其他施加的应激源对噬菌体释放没有显著影响。
