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As a commonly pathogenic bacterium, the rapid detection of Salmonella outbreaks and assurance of food safety require a highly efficient detection method. Herein, a novel approach to Salmonella detection using quantum dot-labeled phage-encoded RBP 55 as a fluorescent nanoprobe is reported. RBP 55, a novel phage receptor binding protein (RBP), was identified and characterized from phage STP55. RBP 55 was functionalized onto quantum dots (QDs) to form fluorescent nanoprobes. The assay was based on the combination of immunomagnetic separation and RBP 55-QDs, which formed a sandwich composite structure. The results showed a good linear correlation between the fluorescence values and the concentration of Salmonella (10 1 -10 7 CFU/mL) with a low detection limit of 2 CFU/mL within 2 h. The method was used to successfully detect Salmonella in spiked food samples. This approach can be used for the simultaneous detection of multiple pathogens by labeling different phage-encoded RBPs using polychromatic QDs in the future., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Biofilm, as a complex microbial community, is a serious and major safety concern in the food industry. Interestingly, some phages could effectively disrupt biofilms. This study characterized a novel isolated Salmonella bacteriophage T102, and its ability to control and remove biofilm produced by multidrug-resistant Salmonella. Phage T102 exhibited a broad host range within the Salmonella genus, especially drug-resistant Salmonella. The genome of phage T102 was comprised of 41,941 bp with 49.7% G + C composition, and with no genes associated with antibiotic resistance or virulence factors. The structural protein profile of phage T102 was subjected to SDS-PAGE and UPLC-MS/MS analysis, among them, 34 peptides were consistent with the hypothetical protein sequences annotated in the genome of T102. The biofilm inhibition assay revealed that phage T102 inhibited the formation of 6 h biofilms by two multidrug-resistant S. Typhimurium strains by 43.17 and 32.42%, respectively. 24 h biofilms formed by S. Typhimurium decreased by 54.94 and 53.67%, respectively, after 2 h of exposure to phage T102. Microscopic observation confirmed the inhibition effect of phage T102 on biofilm formation on spiked lettuce. Overall, our results support new research into the application of bacteriophage for biofilm reduction., Competing Interests: Declaration of Competing Interest The authors have declared no conflict of interest., (Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)

Salmonella and Escherichia coli are important foodborne pathogens, forming bacterial biofilms that contribute to their virulence, antimicrobial resistance, and survival on surfaces. Broad lytic phages are promising alternatives to conventional technologies for pathogen biocontrol and reducing biofilms. Herein, we isolated and characterized a novel polyvalent phage STP55 that not only lyse some serotypes of Salmonella, but also some E. coli strains. It had a wide range of pH (4-12) and thermal (30-60 °C) tolerances. The latent time was determined to be 10 min in the one-step growth experiment. Morphological observations by transmission electron microscopy and phylogenetic analysis using terminase gene classified STP55 to family Ackermannviridae in the order Caudovirales, with a complex tail structure. The genome was found to comprise 157,708 bp double-stranded DNA, with 44.57% GC content, 207 predicted ORFs and with no genes associated with antibiotic resistance, toxins, lysogeny, and virulence factors. Particularly, phage STP55 was able to inhibit single- and dual-species biofilms formation by S. Typhimurium ATCC 14028 and E. coli O157: H7, with a reduction percentage of 51.0%, 47.8% and 52.8%, respectively. Moreover, more than 65.0%, 72.9% and 46.2% of an established, single- and dual-species biofilms by S. Typhimurium ATCC 14028 and E. coli O157: H7 were removed after 8 h exposure to the phage STP55, respectively. The elimination effect of STP55 on dual-species biofilm formed on lettuce was further observed by SEM. Overall, our results demonstrated that STP55 is a promising antimicrobial against Salmonella and E. coli., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Recently, using bacteriophages as new molecular probes in reliable platforms for the detection of bacterial pathogens has attracted more and more increasing attentions. In this paper, a novel isolated Myoviridae bacteriophage SEP37 was covalently immobilized onto gold nanoparticles (AuNPs) modified gold disk electrode (GDE) surfaces using cysteamine (Cys) as a crosslinker. Substrates of GDE-AuNPs-Cys-Phage SEP37 and specific capture of Salmonella cells had been characterized using scanning electron microscopy (SEM) separately. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to study the electrochemical response of the biosensor interface manufacturing and bacterial capture process. Under the optimal experimental conditions, this phage-based EIS biosensor was able to detect Salmonella with a wide linear range from 2 × 10 1 to 2 × 10 6 colony forming unit (CFU)/mL within 30 min in spiked lake water and lettuce samples, with a limit of detection (LOD) of 17 CFU/mL. The detection linear range of spiked chicken samples was 2 × 10 2 to 2 × 10 5 CFU/mL, with a LOD of 1.3 × 10 2 CFU/mL. In combination with a pre-enrichment process for 3.5 h, this assay could reach a LOD of 1 CFU/mL in chicken breast meat samples. Besides, this phage-based EIS biosensor provided good reproducibility and stability. This phage-based EIS biosensor opens a new opportunity for the detection of pathogenic bacteria using the inherent selectivity of bacteriophage recognition., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Salmonella is a globally distributed zoonotic pathogen. Among them, S. pullorum is a host-specific pathogen that seriously affects the development of the poultry breeding industry in China. It mainly infects chickens and can cause white scabs, and the mortality rate after infection is almost 100%. As antibiotics are widely used in animal feed and other production processes, Salmonella resistance has gradually increased. Therefore, there is an increasing need to develop new technologies to control multi-drug resistant (MDR) pathogens and confirm their actual effectiveness in the target food matrix. Bacteriophage can efficiently and specifically lyse bacteria, and will be a potential bactericide to replace antibiotics. In this study, 34 strains of Salmonella bacteriophages were isolated from environmental resources. Therein, phage Pu20 with the widest host spectrum had the strongest ability to lyse tested Salmonella strains. Further studies showed that Pu20 had high pH tolerance and heat resistance, short incubation period. Pu20 can effectively inhibit the growth of two strains of MDR Salmonella in liquid egg white and yolk at 4 °C and 25 °C, respectively. According to morphological and phylogenetic analysis, Pu20 belongs to the Podoviridae family. Genomic analysis of Pu20 indicates a linear 59435 bp dsDNA sequence with no homology to virulence or antibiotic resistance-related genes. Together, these results sheds light on the potential biocontrol application value of Pu20 in food products. [ABSTRACT FROM AUTHOR]