Assessment of antibacterial and quorum quenching activities of yeasts for the biocontrol of enteropathogenic bacteria

Considering increasing antimicrobial resistance and the demand for natural biocontrol agents, yeasts have emerged as potential candidates for combating pathogenic bacteria in agricultural and livestock settings. This study assessed the antimicrobial activity of 52 yeast accessions by evaluating key phenotypes for the biocontrol of Salmonella enterica subsp. enterica serovar Typhimurium and Escherichia coli O157. To enhance the possibility of identifying yeasts with antimicrobial activity, modified yeast extract–malt agar (MYM) and yeast extract–peptone–glycerol agar (MYPG) were employed for yeast cultivation, whereas Reasoner's 2A semisolid agar (R2A) and iron-limited media were used to support pathogen growth. Thirty-one accessions exhibited antimicrobial properties. MYM agar was found to better exhibit the antimicrobial activity of yeasts compared to MYPG agar, with differences (P < 0.05) in inhibition zone sizes and a higher number of accessions showing activity. The efficacy was further enhanced when enteropathogens were cultured on R2A. Comparison of 28S rRNA or 5.8 rRNA genes DNA sequences with the NCBI nucleotide database and phylogenetic analysis identified yeast accessions belonging to seven genera: Candida , Debaryomyces , Metchnikowia , Meyerozyma , Naganishia , Pichia , and Wickerhamomyces . Supernatants from eight selected yeast accessions inhibited biofilm formation in S . Typhimurium and E. coli O157 by up to 30 % and 58 % (P < 0.05), respectively. Furthermore, the presence of quorum quenching molecules was detected by violacein inhibition in Chromobacterium violaceum cultures. Compared to other yeasts (P < 0.05), the adaptability of Pichia sp. accessions was highlighted by their superior growth performance across a range of temperature, pH, and glucose concentration conditions. Moreover, data integration through a composite index facilitated the identification of Pichia sp., Metchnikowia sp., and Meyerozyma sp. accessions as the most promising candidates for a bioproduct. Their high adaptability to stress conditions and growth inhibition of enteropathogens make them suitable active ingredients for bioproducts required in agricultural and livestock settings.