Salmonella is responsible for a wide range of infections and is a constant threat to public health, particularly in light of emerging antibiotic resistance. The use of bacteriophages and phage endolysins as specific antibacterial agents is a promising strategy to control this bacterial infection. Endolysins are important proteins during the process of bacteria lysis by bacteriophages. In this study, we identify a novel endolysin, named LysSE24. LysSE24 was predicted to possess N-acetylmuramidases activity, with a molecular mass of ca. 17.4 kDa and pI 9.44. His-tagged LysSE24 was heterologously expressed and purified by Ni-NTA chromatography. LysSE24 exhibited optimal bactericidal activity against Salmonella Enteritidis ATCC 13076 at a concentration of 0.1 μM. Salmonella population (measured by OD_{600 nm}) decreased significantly (p < 0.05) after 10 min of incubation in combination with the outer membrane permeabilizer in vitro. It also showed antibacterial activity against a panel of 23 tested multidrug-resistant Salmonella strains. Bactericidal activity of LysSE24 was evaluated in terms of pH, temperature, and ionic strength. It was very stable with different pH (4.0 to 10.0) at different temperatures (20 to 60 °C). Both K⁺ and Na⁺ at concentrations between 0.1 to 100 mM showed no effects on its bactericidal activity, while a high concentration of Ca²⁺ and Mg²⁺ showed efficacy. Transmission electron microscopy revealed that exposure to 0.1 μM LysSE24 for up to 5 min caused a remarkable modification of the cell shape of Salmonella Enteritidis ATCC 13076. These results indicate that recombinant LysSE24 represents a promising antimicrobial activity against Salmonella, especially several multidrug-resistant Salmonella strains. Further studies can be developed to improve its bactericidal activity without the need for pretreatment with outer membrane-destabilizing agents by synthetic biology methods.

Mycotoxins are the toxic secondary metabolites produced by fungi and they are a worldwide public health concern. A VHH antibody (or nanobody) is the smallest antigen binding entity and is produced by heavy chain only antibodies. Compared with conventional antibodies, VHH antibodies overcome many pitfalls typically encountered in clinical therapeutics and immunodiagnostics. Likewise, VHH antibodies are particularly useful for monitoring mycotoxins in food and feedstuffs, as they are easily genetic engineered and have superior stability. In this review, we summarize the efforts to produce anti-mycotoxins VHH antibodies and associated assays, presenting VHH as a potential tool in mycotoxin analysis.

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.