Viable but Non-Culturable (VBNC) Bacteria Threaten Food Safety

In 1982, the presence of viable but non-culturable (VBNC) bacteria was first discovered with supporting evidence in Escherichia coli (E. coli) and Vibrio cholerae (V. cholerae) [1]. Ever since then, the reliability of using conventional cell culture-based detection methods such as direct plating and most probable number (MPN) as indicators of pathogenic contamination have been challenged [2]. More recent studies show that VBNC foodborne pathogens pose a serious threat to food safety and public health [3].

Hidden Threat: The VBNC State in Bacteria and Its Impact on Food Safety

VBNC is a dormant state that bacteria enter in response to adverse environmental conditions, such as low temperature, high pressure, or disinfection treatments. As such, they lose their ability to form colonies on conventional culture media. However, they remain alive and potentially infectious, and when conditions are more favorable, the bacteria can recover from the VBNC state and lead to potential bacterial diseases outbreaks. Therefore, traditional culture-based testing methods may underestimate the microbial risk of food products and give false negative results.

To overcome this challenge, quality control (QC) managers need a reliable and rapid method to detect and quantify VBNC cells. One of the promising techniques is flow cytometry (FCM), which can measure the physiological parameters of individual cells based on their light scattering and fluorescence properties. FCM can distinguish between dead and VBNC cells by using different fluorescent dyes or probes that target specific cell components or functions. The advantages of applying FCM-based methods for VBNC detection and quantification in the food industry have been demonstrated by several studies in literature [4]. For instance, FCM has been recommended for the detection of VBNC cells in complex water matrixes such as the process wash water (PWW) from the fruit and vegetable industry, and FCM was found to be more suitable than viability qPCR for this purpose as it avoided the interferences caused by the complex composition of the water matrix [5]. 

Advancing Food and Water Safety with rqmicro.COUNT

rqmicro.COUNT is a compact and easy-to-use flow cytometer that can help solve the problem of VBNC in the area of water and food safety. It can provide accurate and reproducible Intact Cell Count (ICC), which detects all viable cells including VBNC cells, in less than one hour, without the need for complex sample preparation or extensive training. rqmicro.COUNT can also detect specific pathogens like E. coli and Legionella, using different test kits accordingly. For researchers, rqmicro.COUNT is a powerful tool to study the VBNC phenomenon and the conditions that can induce cells to enter VBNC states. For customers in the food and beverage (F&B) industry, rqmicro.COUNT can help them optimize their processing and preservation methods to prevent or reduce the formation of VBNC cells. For example, customers can adjust the temperature, pH, chlorine concentration, or pressure of their process wash water to avoid inducing VBNC state in pathogenic bacteria. By doing so, customers can improve their product safety and shelf life, reduce their waste, and recall costs, and enhance their brand reputation. 

In conclusion, rqmicro.COUNT is a user-friendly and cost-effective flow cytometer that can provide fast and accurate results for VBNC detection and quantification in complex water matrices. With rqmicro.COUNT, industry professionals and scientists can improve their understanding of VBNC phenomenon and together enhance food safety management. Contact us today and let rqmicro.COUNT benefit your work.


[1]  Xu H.S., Roberts N., Singleton F.L. et al. Survival and viability of nonculturable Escherichia coli and Vibrio cholerae in the estuarine and marine environmentMicrob Ecol 8, 313–323 (1982).

[2]  Zhao X, Zhong J, Wei C, Lin CW, Ding T. Current Perspectives on Viable but Non-culturable State in Foodborne Pathogens. Front Microbiol. 2017 Apr 4;8:580. doi: 10.3389/fmicb.2017.00580. PMID: 28421064; PMCID: PMC5378802.

[3] Zhang J, Yang H, Li J, Hu J, Lin G, Tan BK, Lin S. Current Perspectives on Viable but Non-Culturable Foodborne Pathogenic Bacteria: A Review. Foods. 2023; 12(6):1179.

[4] Léonard L., Bouarab Chibane L., Ouled Bouhedda B. et al. Recent Advances on Multi-Parameter Flow Cytometry to Characterize Antimicrobial Treatments. Volume 7 - 2016. 08 August 2016.

[5] Truchado P., Gil I.M., Larrosa M., Allende A. Detection and Quantification Methods for Viable but Non-culturable (VBNC) Cells in Process Wash Water of Fresh-Cut Produce: Industrial Validation. Volume 11 - 2020. 04 May 2020.

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