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From the farm to the dining table, foodborne pathogenic bacteria can contaminate food at any stage of the food production, processing, delivery, preparation, and consumption chain, posing a critical threat to the safety of food systems worldwide [...]

Staphylococcus aureus biofilm is a common bio-contaminant source that leads to food cross-contamination and foodborne disease outbreaks. Hence, there is a need for searching novel antibiofilm agents with potential anti-virulence properties to control S. aureus contamination and infections in food systems. In this study, the antibiofilm effects of lactobionic acid (LBA) against S. aureus and its influence on virulence were explored. The minimum inhibition concentration of LBA on S. aureus was 8 mg/mL. Viable count and crystal violet assays revealed that LBA inhibited and inactivated S. aureus biofilms. Microscopic observations further confirmed the antibiofilm activity of LBA on S. aureus that disrupted the biofilm architecture and inactivated the viable cells in biofilms. Moreover, LBA decreased the release of extracellular DNA (eDNA) and extracellular polysaccharide (EPS) in S. aureus biofilms. LBA suppressed biofilm formation by intervening metabolic activity and reduced virulence secretion by repressing the hemolytic activity of S. aureus. Furthermore, LBA altered the expressions of biofilm- and virulence-related genes in S. aureus, further confirming that LBA suppressed biofilm formation and reduced the virulence secretion of S. aureus. The results suggest that LBA might be useful in preventing and controlling biofilm formation and the virulence of S. aureus to ensure food safety.

Lactobionic acid (LBA) has demonstrated antibacterial activities against multiple foodborne bacteria; however, few studies have reported on its effect against Cronobacter sakazakii. In this study, the antibacterial activity and mode of LBA against C. sakazakii were explored. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of LBA against C. sakazakii were 12.5 and 25 mg/mL, respectively. LBA exhibited bacteriostatic activity at sub-MIC and bactericidal activity at concentrations ≥ MIC. Alkaline phosphatase (AKP) activity, cell outer membrane (OM) permeability, protein leakage, and gel electrophoresis results suggested that LBA increased the permeability of the cell wall and OM, leading to intracellular protein leakage and a decrease in protein contents and activity, indicating LBA damage to the cell wall and membrane. Among these, the rapid AKP activity surge reached 4.37 U/gprot at 2 MIC, and the OM permeability dramatically increased up to 10 min and stabilized after 30 min. Microscopic observations confirm the disruption to the cell wall and membrane, further showing that LBA disrupted the integrity of the cell wall and membrane. Moreover, LBA disturbs normal cellular functions by binding to deoxyribonucleic acid (DNA), as reflected by the competitive binding assay. Overall, LBA possesses potential multiple applications in the food industry due to its natural and antibacterial properties.

Staphylococcus aureus biofilms are a serious problem in the food industry. Wall teichoic acid (WTA) is crucial in S. aureus biofilm formation. Overexpression of the WTA-hydrolyzing enzyme glycerophosphoryl diester phosphodiesterase (GlpQ), induced by lactobionic acid (LBA), may be related to biofilm formation. We investigated the relationship between the regulation on GlpQ degradation of WTA by LBA and S. aureus biofilm formation. LBA minimum inhibitory concentration for S. aureus was 12.5 mg/mL. Crystal violet staining revealed the LBA-mediated inhibition of S. aureus adhesion and biofilm formation. RT-qPCR revealed the repressed expression of adhesion-related genes by LBA. Scanning electron microscopy revealed the obvious disruption of S. aureus surface structure, confirming the repression of S. aureus adhesion and biofilm formation by LBA. Native-PAGE results suggested that the WTA content of S. aureus was reduced under the inhibition of LBA. Additionally, LBA induced the overexpression of glpQ. Combined with our previous work, these results suggest that glpQ is induced in S. aureus to function in WTA degradation with the addition of LBA, resulting in decreased WTA content and subsequent reduction of adhesion and biofilm formation. The findings provide new insight into the degradation mechanism of S. aureus WTA and indicate the potential of LBA as an anti-biofilm agent.

Amino acids are ubiquitous components of bovine milk. However, systematic analyses of the full spectrum of amino acids in different domains of bovine colostrum and mature milk are relatively scarce. Using metabolomics methods based on iTRAQ combined with HPLC–MS/MS, we analyzed free amino acids in bovine colostrum (FBC) and bovine mature milk (FBM), and insoluble-proteome amino acids in bovine colostrum (IPBC) and bovine mature milk (IPBM). Overall, 33, 31, 29, and 30 amino acids were identified in FBC, FBM, IPBC, and IPBM, respectively. Additionally, 28 and 12 significantly different amino acids were found in the FBC vs. FBM and IPBC vs. IPBM groups, respectively, as well as 38 and 28 significantly different metabolic pathways. The free and insoluble-proteome amino acid profiles differed notably between different lactation stages, and their combination provides a better understanding of the biochemical processes in bovine milk. These results enhance our understanding of amino acids in the different domains of bovine colostrum and mature milk, and provide research directions for the development of milk powder.

Staphylococcus aureus can contaminate food products and persist in food-related environments, posing significant challenges to food safety and public health. However, the role of plasmids in mediating antimicrobial resistance (AMR) and facilitating host adaptation in S. aureus has been largely underestimated. We conducted a global plasmidome analysis of 1395 isolates (human: 88.2%, animal: 11.8%) spanning 90 years. Plasmids were detected in 66.8% of strains, typically one to two per genome. We identified 35 distinct plasmid-borne antimicrobial resistance genes (ARGs), with a significant temporal increase in their abundance. Over 85.5% of these plasmids were predicted to be mobilizable, indicating a high transmission potential. Notably, clonal complex 5 (CC5) carried the highest plasmid burden, particularly subclade CC5.6, which exhibited high prevalence of conjugative pSK41 plasmids and ARGs. Although this lineage has not been reported elsewhere, its emergence raises concerns about ARG dissemination through conjugative plasmids. These findings emphasize the role of plasmids in the global spread of AMR and have important implications for food safety and resistance control strategies in food production.

Staphylococcus aureus biofilms are a serious problem in the food industry. Wall teichoic acid (WTA) is crucial in S. aureus biofilm formation. Overexpression of the WTA-hydrolyzing enzyme glycerophosphoryl diester phosphodiesterase (GlpQ), induced by lactobionic acid (LBA), may be related to biofilm formation. We investigated the relationship between the regulation on GlpQ degradation of WTA by LBA and S. aureus biofilm formation. LBA minimum inhibitory concentration for S. aureus was 12.5 mg/mL. Crystal violet staining revealed the LBA-mediated inhibition of S. aureus adhesion and biofilm formation. RT-qPCR revealed the repressed expression of adhesion-related genes by LBA. Scanning electron microscopy revealed the obvious disruption of S. aureus surface structure, confirming the repression of S. aureus adhesion and biofilm formation by LBA. Native-PAGE results suggested that the WTA content of S. aureus was reduced under the inhibition of LBA. Additionally, LBA induced the overexpression of glpQ. Combined with our previous work, these results suggest that glpQ is induced in S. aureus to function in WTA degradation with the addition of LBA, resulting in decreased WTA content and subsequent reduction of adhesion and biofilm formation. The findings provide new insight into the degradation mechanism of S. aureus WTA and indicate the potential of LBA as an anti-biofilm agent.