The Effect of Stressful Conditions on Culturability of Listeria monocytogenes in Food Matrix

L. monocytogenes is a foodborne pathogen which has a high ability for adapting to unfavorable conditions and is able to growth at refrigerator temperature. An important subject about these bacteria is entering into Viable but non-culturable (VBNC) state under stress. The aim of the present study is considering the culturability of this pathogen under refrigeration (4°C) in rainbow trout fillet matrix. For this purpose bacteria was considered in four treatments: starvation at refrigerator temperature, starvation and high salinity at refrigerator temperature, fish fillet matrix at refrigerator temperature and salted fish fillet matrix at refrigerator temperature during time period by standard cultural methods and 16SrRNA gene expression. The obtained results showed that starvation at refrigerator temperature and high salinity at refrigerator temperature treatments lost their culturability at 13 and 27 days, respectively. The results of gene expression of these bacteria also showed they enter in to viable but non culturable state. The results of fish fillet matrix at refrigerator temperature and fish fillet matrix at refrigerator temperature treatments showed that these bacteria in fish fillet matrix at refrigerator temperature keep their culturability and did not enter in to viable but non-culturable state. Regarded to obtained results in this study could conclude that there is the entering possibility of L. monocytogenes in to VBNC state at refrigerator temperature in view point of bacteria environment and it is necessary to review the microbial quality control methods for refrigeration products.