An Alternative to Antibiotics: Selected Methods to Combat Zoonotic Foodborne Bacterial Infections

Pathogenic bacteria contaminating food or animal feed cause serious economic losses in the health sector as well as is in the agriculture and food industry. The development of bacterial resistance due to the misuse of antibiotics and chemicals, especially in the farm industry, can bring dangerous effects for the global population therefore new safe biological antimicrobial solutions are urgently needed. In this paper, we investigate biological alternatives to antibiotics against foodborne pathogens. The most promising alternatives include antimicrobial proteins, bacteriophages, probiotics, and plant-based substances. Each described group of substances is efficient against specific foodborne bacteria and has a preferred use in an explicit application. The advantages and drawbacks of each method are outlined in the final section. Biological antibacterial solutions are usually easily degradable. In contrast to antibiotics or chemical/physical methods, they are also far more specific. When introducing new antibacterial methods it is crucial to check their safety and ability to induce resistance mechanisms. Moreover, it is important to assess its activity to inhibit or kill in viable but nonculturable cells (VBNC) state and biofilm forms. VBNC bacteria are considered a threat to public health and food safety due to their possibility of remaining viable and virulent. Biological alternatives to antibiotics complete the majority of the advantages needed for a safe and efficient antimicrobial product. However, further research is necessary to fully implement those solutions to the market.

ANALYSIS OF THE EFFECT OF PHAGES ON BACTERIA AND THEIR VIABLE BUT NONCULTURABLE CELLS

The growth in the use of antibiotic and chemical substances in meat processing plants shows the need to search for alternative means of decontamination, the most promising of which are bacteriophages. However, there are a lot of little-studied questions on their use, one of which is the effect of bacteriophages on viable but nonculturable (VBNC) cells of bacteria. In this regard, the article provides data on the analysis of the activity of commercial bacteriophages in relation to bacteriacontaminants of raw materials of animal origin, in particular E. coli and Salmonella enterica typhimurium, as well as their VBNC-cells.

SIGNIFICANCE OF VIABLE BUT NONCULTURABLE BACTERIA FOR SAFETY OF FOOD PRODUCTS

In this review data on hazardous influence of nonculturable cells of pathogens on humans and animals, of contamination of foodstuffs is presented and also attention is stressed on properties of such cells and their effect through foodstuffs on humans and animals. Main hypothesis of formation and resuscitation of viable but nonculturable cells are elucidated. Factors that influence shifting bacteria to nonculturability and their conversion into active state are discussed. The conclusion is drawn about biohazard of viable nonculturable cells and insufficient data about their physiology and mechanisms of transition into this state and resuscitation back.

Sizing Up the Uncultured Microbial Majority

ABSTRACTPredicting the total number of microbial cells on Earth and exploring the full diversity of life are fundamental research concepts that have undergone paradigm shifts in the genomic era. In this issue, Lloyd and colleagues (K. G. Lloyd, A. D. Steen, J. L. Ladau, J. Yin, and L. Crosby, mSystems 3:e00055-18,https://doi.org/10.1128/mSystems.00055-18, 2018) present results that combine these two concepts by estimating the total diversity of all cells from Earth’s environments. Leveraging publicly available amplicon, metagenomic, and metatranscriptomic datasets, they determined that nearly all environments are dominated by uncultured lineages, with the exception of humans and human-associated habitats. They define a new concept: phylogenetically diverse noncultured cells (PDNC). Unlike viable but nonculturable cells (VBNC), PDNC are microorganisms for which traditional isolation techniques may never succeed. Lloyd et al. estimate that the majority of microorganisms in Earth’s ecosystems may be PDNC and conclude that culture-independent methods combined with innovative culturing techniques may be required to understand the ecology and physiology of these abundant and divergent microorganisms.

Analysis of the Resuscitation-Availability of Viable-But-Nonculturable Cells ofVibrio parahaemolyticusupon Exposure to the Refrigerator Temperature

ABSTRACTMajor pathogenic strains ofVibrio parahaemolyticuscan enter into the viable-but-nonculturable (VBNC) state when subjected to environmental conditions commonly encountered during food processing. Especially, VBNC cells can be recovered to the culturable state reversibly by removing the causative stress, expressing higher levels of virulence factors. Therefore, the aim of this study was to determine if VBNCV. parahaemolyticusstrains retain the resuscitation-availability upon eliminating the adverse condition, followed by the enrichment in developed resuscitation-facilitating buffers. Bacterial cells were shown to enter into the VBNC state in artificial sea water (ASW, pH 6) microcosms at 4°C within 70 days. VBNC cells were harvested, inoculated in formulated resuscitation-buffers, and then incubated at 25°C for several days. TSB (pH 8) supplemented with 3% NaCl (TSBA) exhibited the higher resuscitation-availability of VBNC cells. It was also shown that TSBAcontaining 10,000 U/mg/protein catalase, 2% sodium pyruvate, 20 mM MgSO4, 5 mM ethylenediaminetetraacetic acid (EDTA), and cell free supernatants extracted from the pure cultures ofV. parahaemolyticuswas more effective in resuscitating VBNC cells ofV. parahaemolyticus, showing by 7.69-8.91 log10CFU/ml.IMPORTANCEGenerally, higher concentrations (≤40%) of NaCl are used for preserving different sorts of food products from bacterial contaminations. However, it was shown from the present study that strains ofV. parahaemolyticuswere able to persist in maintaining the cellular viability, thereby entering into the VBNC state upon exposure to the refrigerator temperature for 80 days. Hence, the ability of VBNCV. parahaemolyticusto re-enter into the culturable state was examined, using various resuscitation buffers that were formulated in this study. VBNC cells re-gained the culturability successfully when transferred onto the resuscitation-buffer D, and then incubated at 25°C for several days. Resuscitation-facilitating agent D is consisting of antioxidizing agents, mineral, an emulsifier, and cell free supernatants from the actively growing cells ofV. parahaemolyticus. It appeared that such a reversible conversion of VBNC cells to the culturable state would depend on multiple resuscitation-related channels.