This study aimed to identify and characterize lactic acid bacteria strains with antimicrobial activity against Proteus mirabilis, a gram-negative bacterium associated with Parkinson’s disease, Crohn’s disease, and nosocomial infections. Among the 987 lactic acid bacteria strains isolated from various sources, strain no. CHK903 showed high antimicrobial activity against P. mirabilis. Phylogenetic tree analysis based on the 16S rRNA gene and scanning electron microscope analysis identified the selected strain as the rod-shaped Weissella cibaria. The culture supernatants of W. cibaria CHK903 showed antimicrobial activity against some pathogens. Two antimicrobial compounds with molecular weights 189 and 365 Da were partially purified from the culture supernatants of W. cibaria CHK903 using Biogel P2 gel permeation column chromatography. The culture supernatants of W. cibaria CHK903 also showed significant antibiofilm properties, inhibiting biofilm formation by 90% and removing pre-formed biofilms by 60%. These findings suggest the potential therapeutic use of W. cibaria CHK903 as a natural antimicrobial against P. mirabilis-related infections.

Dental caries is an infectious disease accompanied by the destruction of teeth. It is a multifactorial disease caused by the interaction between microbes in dental plaque and food, with cariogenic Streptococcus mutans being one of the primary causes. In this study, the antimicrobial and antibiofilm activities of Lactiplantibacillus plantarum THK-j112 isolated from Kimchi, a traditional fermented food, against S. mutans were investigated. Furthermore, this paper also showed the possibility of developing this strain. After analyzing the 16S rRNA sequence, strain THK-j112 was named L. plantarum THK-j112 as it shared 99.93% similarity with L. plantarum ATCC 14917T. Both L. plantarum THK-j112 and L. plantarum ATCC 14917T demonstrated MIC values of 5 mg/mL and MBC values of 10 mg/mL against S. mutans KACC 16833T. The study confirmed that L. plantarum THK-j112 exhibited significant concentration-dependent inhibitory effects on biofilm formation, acid production, and glucosyltransferases(GTFs) production. Regarding hemolytic activity, Bacillus cereus ATCC 14579T, used as a positive control, was confirmed to cause hemolysis, whereas L. plantarum THK-j112 did not cause this phenomenon. Additionally, except for gentamicin, the antibiotic resistance test revealed a lower value than the MIC cut-off value for each antibiotic, indicating no resistance. Based on the findings, L. plantarum THK-j112 is expected to be useful in the food industry, such as functional food, as a lactic acid bacterium with antimicrobial and antibiofilm effects.