Effectiveness of a Phage Cocktail as a Potential Biocontrol Agent against Saprophytic Bacteria in Ready-To-Eat Plant-Based Food

Abstract

This study aimed to evaluate the effectiveness of the phage cocktail to improve the microbiological quality of five different mixed-leaf salads: rucola, mixed-leaf salad with carrot, mixed-leaf salad with beetroot, washed and unwashed spinach, during storage in refrigerated conditions. Enterobacterales rods constituted a significant group of bacteria in the tested products. Selected bacteria were tested for antibiotic resistance profiles and then used to search for specific bacteriophages. Forty-three phages targeting bacteria dominant in mixed-leaf salads were isolated from sewage. Their titer was determined, and lytic activity was assessed using the Bioscreen C Pro automated growth analyzer. Two methods of phage cocktail application including spraying, and an absorption pad were effective for rucola, mixed leaf salad with carrot, and mixed leaf salad with beetroot. The maximum reduction level after 48 h of incubation reached 99.9% compared to the control sample. In washed and unwashed spinach, attempts to reduce the number of microorganisms did not bring the desired effect. The decrease in bacteria count in the lettuce mixes depended on the composition of the autochthonous saprophytic bacteria species. Both phage cocktail application methods effectively improved the microbiological quality of minimally processed products. Whole-spectral phage cocktail application may constitute an alternative food microbiological quality improvement method without affecting food properties.

Newly Isolated Virulent Salmophages for Biocontrol of Multidrug-Resistant Salmonella in Ready-to-Eat Plant-Based Food

“…The bacterial strains have been isolated and deposited in the Culture Collection of Industrial Microorganisms—Microbiological Resources Center (IAFB). The taxonomic identification of most of the bacteria used was determined during previous studies or in this study, in accordance with the procedure described in our articles [ 14 , 87 ]. Moreover, the Salmonella strains were sent to the National Salmonella Center (Medical University of Gdańsk, Gdansk, Poland) for serotyping.…”

Biological Characterization and Genomic Analysis of Three Novel Serratia- and Enterobacter-Specific Virulent Phages

“…Twenty-five strains from the Enterobacterales order were used to determine the host range of newly isolated phages. This bacterial host range was also checked in the study by Wójcicki and co-workers [ 39 ] to determine the effectiveness of a phage cocktail for biocontrol against saprophytic bacteria in ready-to-eat plant-based food [ 39 ]. The results obtained for Serratia phage KKP_3708, Serratia phage KKP_3709, Enterobacter phage KKP_3711 and the calculated efficiency of plating (EOP) are presented in Table 1 .…”

“…The difficulty in eliminating S. liquefaciens , S. marcescens and E. cloacae lies in the ability of these bacteria to secrete extracellular polymers, which allows the creation of dense biofilms that protect bacterial cells against environmental factors and hinders their elimination from raw materials and surfaces of food production lines [ 21 , 35 , 36 ]. A promising technique for extending the shelf life of food is the use of strictly lytic bacteriophages or their enzymes, which do not affect the nutritional value of the product and do not change the sensory characteristics [ 37 , 38 , 39 ]. Before practical application in biocontrol or phage therapy, a comprehensive characterization of bacteriophages is needed.…”

Antibiotic Resistance: Do We Need Only Cutting-Edge Methods, or Can New Visions Such as One Health Be More Useful for Learning from Nature?

“…Phage cocktails were applied through spraying or an absorption pad with a 100% reduction level of bacterial contaminants compared to a control sample after 48 h of incubation in the mixed-leaf salads, but a lack of effect in spinach samples may have been due to different bacterial species involved. A whole-spectrum phage cocktail application may constitute an alternative food microbiological quality improvement method without affecting food properties [45]. It is noteworthy that reducing contamination without the complete elimination of contaminant bacteria can be an efficacious method of assuring food safety regardless since bacterial load is important in disease evolution.…”