Salmonella Typhimurium DT 104 response to Lytic bacteriophage and Lactobionic acid on raw chicken breast

Application of a novel lytic phage to control enterotoxigenic Escherichia coli in dairy food matrices

A novel Escherichia coli phage designated as EC BD was isolated from cattle dung samples. Transmission electron microscopy demonstrated that the morphology of phage EC BD belongs to the family Myoviridae. The efficiency of plating (EOP) and scanning electron microscopy revealed the strong lytic activity of phage EC BD with a large burst size and a short latent period. Whole genome data analysis suggested that phage EC BD was inclined towards being completely lytic and revealed the absence of toxins, virulence and antibiotic resistance genes. Phylogenomic analysis of phage EC BD receptor binding proteins (RBPs) showed 74-100 % similarity with sixteen Enterobacter phages, representing their broad host range. The phage genome contains 262 ORFs, of which 107 displayed a unique pattern and additionally, the presence of a tRNA gene directed their fast replication and high stability. Comparative genome analysis suggested phage EC BD as a novel member of the genus Duplodnaviria and family Myoviridae. The efficiency of phage EC BD was determined in dairy food matrices (milk, cheese and paneer) artificially contaminated with enterotoxigenic E. coli strains ETEC H10407, ETEC K 12S and ETEC PB 176 with a significant reduction of 4.8, 6.0 and 5.3 log CFU/mL in milk and a substantial 4.9, 5.8 and 4.6 log CFU/mL reduction in cheese samples after 6 days at low storage temperature (4 °C); furthermore, within the similar conditions, paneer samples showed 4, 5.1 and 3.5 log CFU/mL reduction. EC BD phage treatment represents the complete eradication of three ETEC strains in liquid and semisolid dairy food matrices. This study suggested that phage EC BD might have potential as a biocontrol approach against ETEC foodborne infections.

Isolation, whole genome sequencing and application of a broad-spectrum Salmonella phage

Salmonella is considered as one of the most common zoonotic /foodborne pathogens in the world. The application of bacteriophages as novel antibacterial agents in food substrates has become an emerging strategy. Bacteriophages have the potential to control Salmonella contamination.We have isolated and characterized a broad-spectrum Salmonella phage, SP154, which can lyse 9 serotypes, including S. Enteritidis, S. Typhimurium, S. Pullorum, S. Arizonae, S. Dublin, S. Cholerasuis, S. Chester, S. 1, 4, [5], 12: i: -, and S. Derby, accounting for 81.9% of 144 isolates. SP154 showed a short latent period (40 min) and a high burst size (with the first rapid burst size at 107 PFUs/cell and the second rapid burst size at approximately 40 PFUs/cell). Furthermore, SP154 activity has higher survival rates across various environmental conditions, including pH 4.0-12.0 and temperatures ranging from 4 to 50 °C for 60 min, making it suitable for diverse food processing and storage applications. Significant reductions in live Salmonella were observed in different foods matrices such as milk and chicken meat, with a decrease of up to 1.9 log10 CFU/mL in milk contamination and a 1 log10 CFU/mL reduction in chicken meat. Whole genome sequencing analysis revealed that SP154 belongs to the genus Ithacavirus, subfamily Humphriesvirinae, within the family Schitoviridae. Phylogenetic analysis based on the terminase large subunit supported this classification, although an alternate tree using the tail spike protein gene suggested affiliation with the genus Kuttervirus, underscoring the limitations of relying on a single gene for phylogenetic inference. Importantly, no virulence or antibiotic resistance genes were detected in SP154. Our research highlights the potential of using SP154 for biocontrol of Salmonella in the food industry.

Isolation and characterization of multidrug-resistant Salmonella-specific bacteriophages and their antibacterial efficiency in chicken breast

The use of phages as biocontrol agents against antibiotic-resistant strains of Salmonella spp. is gaining attention. This study aimed to isolate lytic bacteriophages specific for multidrug-resistant Salmonella enterica serovars Typhimurium; it also evaluated the bactericidal effect of isolated phages (STP-1, STP-2, STP-3, and STP-4) from sewage sample against S. Typhimurium as host strains. Moreover, a current study evaluated the efficacy of a bacteriophage cocktail against S. Typhimurium cocktail in chicken breast meat. The 4 phages were classified under the Caudoviricetes class by morphology characterization. On host range testing, they exhibited lytic activities against S. Typhimurium, S. Enteritidis, and S. Thompson. In the stability test, the phages exhibited resistance to heat (above 70°C for 1 h) and pH (strongly alkaline for 24 h). Additionally, the phages had comparable adsorption rates (approximately 80% adsorption in under 5 min). Additionally, the latent periods ranged from 30 to 50 min, with respective burst sizes of 31, 218, 197, and 218 PFU/CFU. In vitro, bacterial challenge demonstrated that at a multiplicity of infection (MOI) of 10, each phage consistently inhibited S. Typhimurium growth at 37°C for 24 h. In the food test, the phage cocktail (MOI = 1,000) reduced S. Typhimurium in artificially contaminated chicken breast meat stored at 4°C by 0.9 and 1.2 log CFU/g after 1 and 7 d, respectively. The results point toward a promising avenue for addressing the challenge of multidrug-resistant S. Typhimurium in the food industry through the use of recently discovered phages. Notably, the exploration of phage cocktails holds significant potential for combating S. Typhimurium in chicken breast products in the times ahead.

Facial Preparation of Cyclometalated Iridium (III) Nanowires as Highly Efficient Electrochemiluminescence Luminophores for Biosensing

In this study, highly efficient ECL luminophores composed of iridium complex-based nanowires (Ir-NCDs) were synthesized via covalently linking bis(2-phenylpyridine)-(4-carboxypropyl-2,2'-bipyridyl) iridium(III) hexafluorophosphate with nitrogen-doped carbon quantum dots (NCDs). The ECL intensity of the nanowires showed a five-fold increase in ECL intensity compared with the iridium complex monomer under the same experimental conditions. A label-free ECL biosensing platform based on Ir-NCDs was established for Salmonella enteritidis (SE) detection. The ECL signal was quenched linearly in the range of 10²-10⁸ CFU/mL for SE with a detection limit of 10² CFU/mL. Moreover, the relative standard deviations (RSD) of the stability within and between batches were 0.98% and 3.9%, respectively. In addition, the proposed sensor showed high sensitivity, selectivity and stability towards SE in sheep feces samples with satisfactory results. In summary, the excellent ECL efficiency of Ir-NCDs demonstrates the prospects for Ir(III) complexes in bioanalytical applications.

Application of a novel lytic phage vB_EcoM_SQ17 for the biocontrol of Enterohemorrhagic Escherichia coli O157:H7 and Enterotoxigenic E. coli in food matrices

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 and Enterotoxigenic E. coli (ETEC) are important foodborne pathogens, causing serious food poisoning outbreaks worldwide. Bacteriophages, as novel antibacterial agents, have been increasingly exploited to control foodborne pathogens. In this study, a novel broad-host range lytic phage vB_EcoM_SQ17 (SQ17), was isolated, characterized, and evaluated for its potential to control bacterial counts in vitro and in three different food matrices (milk, raw beef, and fresh lettuce). Phage SQ17 was capable of infecting EHEC O157:H7, ETEC, and other E. coli strains. Morphology, one-step growth, and stability assay showed that phage SQ17 belongs to the Caudovirales order, Myoviridae family, and Mosigvirus genus. It has a short latent period of 10 min, a burst size of 71 PFU/infected cell, high stability between pH 4 to 12 as well as thermostability between 30°C and 60°C for 60 min. Genome sequencing analysis revealed that the genome of SQ17 does not contain any genes associated with antibiotic resistance, toxins, lysogeny, or virulence factors, indicating the potential safe application of phage SQ17 in the food industry. In Luria-Bertani (LB) medium, phage SQ17 significantly decreased the viable counts of EHEC O157:H7 by more than 2.40 log CFU/ml (p < 0.05) after 6 h of incubation at 37°C. Phage SQ17 showed great potential to be applied for biocontrol of EHEC O157:H7 in milk and raw beef. In fresh lettuce, treatment with SQ17 also resulted in significant reduction of viable cell counts of EHEC O157:H7 and ETEC at both 4°C and 25°C. Our results demonstrate that SQ17 is a good candidate for application as an EHEC O157:H7 and ETEC biocontrol agent in the processing stages of food production and food preservation.

Salmonella spp. Response to Lytic Bacteriophage and Lactic Acid on Marinated and Tenderized Raw Pork Loins

Bacterial food poisoning cases due to Salmonella have been linked with a variety of pork products. This study evaluated the effects of a Salmonella-specific lytic bacteriophage and lactic acid (LA) on Salmonella Enteritidis, Salmonella Montevideo, and Salmonella Heidelberg growth on raw pork loins. Pork loins were cut into approximately 4 cm thick slices. Pork slices were randomly assigned to five treatment groups (control, DI water, LA 2.5%, phage 5%, and LA 2.5% + phage 5%) with six slices per group per replication. Pork loins were inoculated with 106 CFU/mL of Salmonella spp. and stored at 4 °C for 30 min. After 1 h of treatment application and marination, phage 5% significantly (p < 0.05) reduced the surface bacterial population by 2.30 logs when compared with the control group. Moreover, the combined treatment of LA 2.5% + phage 5% significantly (p < 0.05) reduced the surface bacterial population by more than 2.36 logs after 1 h of marination. In the post-tenderization surface samples, the combination of both phage and LA showed a significant reduction (p < 0.05) when compared with the control group. However, the treatments had no effect (p > 0.05) when analyzing the translocation of pathogens on pork loins.