Significance and Impact of the Study: This study provides new insight into biofilm control strategy based on probiotic approach. Probiotic strains effectively inhibited the biofilm formation of Listeria monocytogenes through the mechanisms of competition, exclusion and displacement. These findings contribute to better understand the probiotic-mediated competition, exclusion and displacement in biofilm formation by pathogens. AbstractThe objective of this study was to examine the inhibitory effect of probiotic strains on pathogenic biofilm formation in terms of competition, exclusion and displacement. Probiotic strains (Lactobacillus acidophilus KACC 12419, Lact. casei KACC 12413, Lact. paracasei KACC 12427 and Lact. rhamnosus KACC 11953) and pathogens (Salmonella Typhimurium KCCM 40253 and Listeria monocytogenes KACC 12671) were used to evaluate the autoaggregation, hydrophobicity and biofilm formation inhibition. The highest auto-aggregation abilities were observed in Lact. rhamnosus (17Á5%), Lact. casei (17Á2%) and Lact. acidophilus (15Á1%). Salm. Typhimurium had the highest affinity to xylene, showing the hydrophobicity of 53Á7%. The numbers of L. monocytogenes biofilm cells during the competition, exclusion and displacement assays were effectively reduced by more than 3 log when cocultured with Lact. paracasei and Lact. rhamnosus. The results suggest that probiotic strains can be used as alternative way to effectively reduce the biofilm formation in pathogenic bacteria through competition, exclusion and displacement.

Aim:  To characterize the cellular and molecular properties of Salmonella Typhimurium exposed to antimicrobials in association with physicochemical property, biofilm formation ability and gene expression patterns. Methods and Results:  The antimicrobial susceptibilities against Salmonella Typhimurium were evaluated to determine the MICs of allyl isothiocyanate (AITC), thymol, eugenol and polyphenol. Cell surface hydrophobicity, aggregation and biofilm formation assays were conducted to assess the physicochemical properties of Salm. Typhimurium treated with sublethal concentrations (SLC2D) of antimicrobials. The expression patterns of adhesion‐related genes (adrA, csgD, fimA and lpfE), virulence‐related genes (hilA and stn) and efflux‐related genes (acrA, acrB, ompD and tolC) were evaluated by real‐time RT‐PCR. Thymol exhibited the highest antimicrobial activity against Salm. Typhimurium planktonic, biofilm and dispersed cells, showing 0·18, 0·96 and 0·42 mg ml−1 of SLC2D values, respectively. The antimicrobial‐treated Salm. Typhimurium showed low hydrophobicity. The highest auto‐aggregation ability (67%) of polyphenol‐treated Salm. Typhimurium was positively associated with the enhanced ability to form biofilms. The csgD, fimA, hilA and lpfE genes were up‐regulated in the polyphenol‐treated Salm. Typhimurium planktonic and biofilm cells. Conclusion:  The results suggest that the antimicrobial resistance and virulence potential varied depending on the physiological states of Salm. Typhimurium during the transition from planktonic to biofilm cell growth. Significance and Impact of the Study:  This study can expand our understanding of cellular and molecular mechanisms of biofilm formation and also provide useful information for reducing biofilm‐associated virulence potential.

This study was designed to evaluate the combined effect of probiotic Lactobacillus rhamnosus and bacteriophage SA11 on the control of antibiotic-sensitive Staphylococcus aureus (ASSA) and antibiotic-resistant S. aureus (ARSA) under the simulated intestinal conditions. The survivability of ASSA and ARSA were determined in the simulated phosphate-buffered saline (PBS)-, trypticase soy broth (TSB)-, and milk-based gastric juices adjusted to pH 2.0, 3.0, and 5.0 at 37 °C for 30 min. The inhibitory effect of bacteriophage SA11 and probiotic on the growth of ASSA and ARSA was evaluated in the simulated intestinal juices at 37 °C for 20 h. The least reductions in the numbers of ASSA and ARSA were observed in the milk-based gastric juices at pH 2.0 (<1 log). No significant changes in the teichoic acid-mediated sliding motility were observed for ASSA and ARSA after 30-min exposure to the simulated gastric juices (pH 2.0, 3.0, and 5.0), responsible for the enhanced bacterial attachment to the epithelial cells. The bacteriophage SA11 was stable down to pH 5.0 and up to 0.06 % bile salts. The bacteriophage SA11 combined with probiotic effectively inhibited the growth of ASSA and ARSA in the simulated intestinal conditions, showing more than 4 log reduction. The relative expression levels of adhesion-related genes (clfA, eno, and fnbA) and efflux-related genes (mdeA, norB, and norC) were less decreased in ARSA than in ASSA after exposure to the simulated gastrointestinal conditions. These results might shed light on the application of bacteriophage to control the ingested antibiotic-resistant foodborne pathogens in the intestinal tract.

The main parts of automobiles are the piston rod of the shock absorber and the steering rack of the steering gear, and their quality control is critical in the product process. In the process line, these products are normally inspected through visual inspection, sampling, and simple tensile tests; however, if there is a problem or abnormality, it is difficult to identify the type and location of the defect. Usually, these defects are likely to cause surface cracks during processing, which in turn accelerate the deterioration of the shock absorber and steering, causing serious problems in automobiles. As a result, the purpose of this study was to present, among non-destructive methods, a shock response test method and an analysis method that can efficiently and accurately determine the defects of the piston rod and steering rack. A test method and excitation frequency range that can measure major changes according to the location and degree of defects were proposed. A defect discrimination model was constructed using machine and deep learning through feature derivation in the time and frequency domains for the collected data. The analysis revealed that it was possible to effectively distinguish the characteristics according to the location as well as the presence or absence of defects in the frequency domain rather than the time domain. The results indicate that it will be possible to quickly and accurately check the presence or absence of defects in the shock absorber and steering in the automobile manufacturing process line in the future. It is expected that this will play an important role as a key factor in building a smart factory.

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