Background: Nonculturable cells are formed under stress. These viable but nonculturable (VBNC) cells retain the ability to revert to active growth and division when conditions become favorable, or after treatment with resuscitating factors. Information about the possible presence of VBNC in bacterial lyophilized probiotic preparations, foodstuffs, live vaccines, etc., indicates that human as well as animal intestines are a significant area for research.Methods: Samples were stored for different periods of time (up to 30 years) according to the manufacturers' manuals. Total counts were conducted using the Goryaev-Thoma counting chamber and actual viability was assessed by luminescence microscopy after staining with Live/Dead® (Baclight™). CFU/ml counts were made using solid or semisolid media. Viable cells that lacked the ability to form colonies were considered VBNC. Results:We studied 11 batches of commercial probiotics (Russia) from different sources, containing lyophilized E. coli, lactobacilli, or bifidobacteria, in ampoules or vials. In E. coli preparations, depending on storage periods, the amounts of VBNC varied from 4.1% (3 years) to 99.7% (30 years) and showed different total viability (52.2 -91.3%), as well as the percentage of VBNC cells. A different sample that had been expired for 11 years was 79.5% NC. It is also noteworthy that the 5-dose vials, 4 years past expiration, from yet another source, showed a higher amount of VBNC cells (85.5%). Two different batches that had been expired for three years contained 4.1 and 21.3% VBNC cells. 4 of the 5-dose vials of lyophilized lactobacilli were not expired and contained 58.8 -80.4% VBNC cells. Total viability varied from 92.9 to 100%, and there was an unmistakable positive correlation between total viability and culturability. The last batch, which had expired 6 years earlier, has 23.7% viable cells and about 98% VBNC. Nonexpired bifidobacterial samples contained 70.7 and 95.5% of viable cells and were 50 and 100% culturable. Conclusion:We demonstrated the presence of VBNC cells in lyophilized probiotic preparations

Review materials on the conducted research and application of bacteriophages as a means of decontamination of food products are presented. Several main examples of the use of bacteriophages are described. It is established that bacteriophages are one of the safest and most environmentally friendly means of disinfection of products. In addition to a short analysis of the results of the use of bacteriophages, further prospects for their use are indicated.

The relevance of the study and the presence of gaps in the relevant knowledge on the topic. Potential existence of hazardous viable but nonculturable (VBNC) cells of pathogenic microorganisms in foodstuffs that can be formed under the influence of various factors, their detection and determination of conditions for formation of VBNC cells of various contaminant bacteria are relevant for preventing contamination of meats.Methods. In the study, a search was conducted for VBNC cells in chicken mince in real time and during experimental infection of it by Staphylococcus aureus 209P. In order to detect VBNC cells in chicken mince, total number of microbes, number of bacterial colonies (CFU), and the portion of living (dead) cells were determined in 1g of the product using a commercial set of fluorescent dyes. A second study was carried out after 5 h of incubation of tested samples at room temperature.Results and discussion. In samples of minced meat on the 4th day after production, more than 99% of all detected living cells were VBNC. After 5-hour incubation of the sample, the number of CFU/g increased by 22.5 times, but the portion of VBNC cells remained higher than 99% of viable bacteria. During artificial infection of the same batch of mince with S. aureus in broth culture at the stage of logarithmic growth, the amount of VBNC cells for 0 hours was 97.3%. After 5 hours their number increased to 99.99%. Probably, in the introduced culture of Staphylococcus at the stage of active reproduction, formation of VBNC bacteria did not occur, which initially reduced their number in the sample. After 5-h incubation, transition of bacteria to VBNC state was accelerated, possibly due to unfavorable conditions for the cell population (changes in trophic substrate, temperature, pH, etc.).Conclusions. Experimental data confirm presence of VBNC bacteria in chicken products that don’t grow on traditional nutrient media, and showing a false negative result in traditional microbiological expertise. Because of the biohazard of such dormant cells, it is advisable to provide regulated testing of foodstuffs for presence of VBNC cells.

Background. It is known that bacteria develop resistance to antibiotics in response to their presence and tend to maintain it for a long time. In addition, microbes can remain viable by passing into an uncultivated state that is not detected by microbiological methods. This state of the population is characterized by cell resistance to various stresses, including the effects of antibiotics.Aim. To study the parameters of transition into an uncultivated state in E.coli M-17 cells resistant to an antibiotic.Material and methods. Resistant E.coli M-17 cells were obtained by culturing the initial population in media with increasing concentrations of ampicillin (up to 50 µg/mL). Seed cultures were prepared from sensitive and resistant substrains, from which the cells were transferred to a hyperosmotic, «starvation» medium — artificial sea water. The resulting populations were incubated for a long time, samples were periodically taken to conduct the assessment of viability parameters.Results. The experiments on long-term incubation of sensitive and resistant populations of E.coli M-17 showed that ampicillin-resistant substrain of the studied culture transitioned into an uncultivated state significantly faster and quantitatively higher than its sensitive variant. The presence of the antibiotic in the inoculum increased the time for the transition of resistant R2 bacteria to a viable uncultivated state to a level of >90% compared to R1. The R1 population at the beginning of the stress exposure massively (up to 77.7%) transitioned into viable but non-culturable cells (VBNCs) in the medium without an antibiotic in a similar seed culture. Periods of cell death were noted during the observation, with those cells becoming a substrate for the living part of the population and could lead to secondary growth of bacteria or partial restoration of dormant cells.Conclusion. Cells resistant to the antibiotic quickly transitioned into the non-culturable state compared to sensitive cells of the studied strain. The addition of an antibiotic to the medium for obtaining a seed culture slowed down the transition of cells to an uncultivated state.

Minced chicken is one of the most popular products on the domestic market. However, it is prone to contamination with opportunistic microorganisms during production process and storage. Thereby the data on the use of bacteriophages, specifically lysing the main contaminants of minced chicken is presented. It is stressed out that they are safe and effective in suppression of growth of contaminating microorganisms. Addition of phages does not influence organoleptic properties of the product.