Jul 31, 2026 - Foods
Listeria can become culturable again after disinfection
A recent study shows that Listeria monocytogenes can survive a disinfection treatment in stainless steel biofilms in a viable but non-culturable state. After transferring to smoked herring, the bacteria became culturable again and multiplied significantly during chilled storage.
Viable but non-culturable cells are referred to as VBNC cells. They are still viable but cannot be detected with conventional cultural examination methods.
For the study, biofilms of Listeria monocytogenes were produced on stainless steel surfaces and treated with a disinfectant based on quaternary ammonium compounds. The treatment significantly reduced the number of culturable cells. At the same time, a significant proportion of the Listeria remained viable. This suggests that the bacteria transitioned into a VBNC state due to disinfection stress.
Subsequently, the researchers brought the treated stainless steel surfaces into contact with smoked, salted herring. Viable Listeria were transferred to the food. The herring pieces were vacuum-packed and stored for seven days at 4°C and another 14 days at 8°C.
After just seven days, culturable Listeria were detectable again. By the end of the 21-day storage period, their number increased to about 10⁵ to 10⁷ CFU/g. However, the researchers point out that the proliferation of individual cells, which may still be culturable at the beginning, cannot be completely ruled out.
The results show that conventional cultural examination methods may underestimate the presence of viable Listeria monocytogenes after a disinfection treatment. Particularly in companies producing ready-to-eat and vacuum-packed foods, effective biofilm prevention, carefully tested cleaning and disinfection procedures, and risk-oriented environmental monitoring are of great importance.
The BAV Institute supports food companies in microbiological testing for Listeria monocytogenes, environmental monitoring, and assessing cleaning and hygiene concepts. Feel free to contact us.
Source:
Brauge, T.; Leleu, G.; Hanin, A. (2026): Viable but Nonculturable Listeria monocytogenes May Resuscitate After Transfer From Stainless Steel Biofilms to Vacuum-Packed Smoked Herring. Journal of Food Protection, Article 100775.
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