Antimicrobial Activity of Six International Artisanal Kefirs against Bacillus cereus, Listeria monocytogenes, Salmonella enterica Serovar Enteritidis, and Staphylococcus aureus

Abstract

Kefir, a fermented dairy beverage, exhibits antimicrobial activity due to many metabolic products, including bacteriocins, generated by lactic acid bacteria. In this study, the antimicrobial activities of artisanal kefir products from Fusion Tea (A), Britain (B), Ireland (I), Lithuania (L), the Caucuses region (C), and South Korea (K) were investigated against select foodborne pathogens. Listeria monocytogenes CWD 1198, Salmonella enterica serovar Enteritidis ATCC 13076, Staphylococcus aureus ATCC 25923, and Bacillus cereus ATCC 14579 were inhibited by artisanal kefirs made with kefir grains from diverse origins. Kefirs A, B, and I inhibited all bacterial indicator strains examined at varying levels, except Escherichia coli ATCC 12435 (non-pathogenic, negative control). Kefirs K, L, and C inhibited all indicator strains, except S. aureus ATCC 25923 and E. coli ATCC 12435. Bacteriocins present in artisanal kefirs were determined to be the main antimicrobials in all kefirs examined. Kefir-based antimicrobials are being proposed as promising natural biopreservatives as per the results of the study.

Metagenomic analysis and antimicrobial activity of two fermented milk kefir samples

“…Also, the E_kefir extracts showed bactericidal activity against the four bacterial strains with no dilution and a dilution of 1:2, considering that no growth of colonies was observed in plates of culture medium seeded in incubation after 24 h. Therefore, C_kefir cell‐free extracts showed increased bactericidal activity against the four bacterial strains, in comparison with the E_kefir extracts, suggesting that C_kefir is more efficient in inhibiting bacterial growth. In this address, antagonistic effects of lactic acid bacteria against Salmonella , Escherichia , Staphylococcus , and Bacillus have been reported (Digaitiene et al, 2012; Iraporda et al, 2017; Kim et al, 2016; Nguyen et al, 2015; Silva et al, 2009; Sindi et al, 2020). Indeed, lactic acid bacteria isolated from kefir reduce Salmonella infection in epithelial cells in vitro (Zavala et al, 2016).…”

“…plantarum , and S . cerevisiae among others (Garofalo et al, 2015; Marsh et al, 2013; Sindi et al, 2020). Nevertheless, we found species not previously reported in kefir, such as Gordonia sp.…”

Bacterial Populations in International Artisanal Kefirs

“…The 16S rRNA gene sequencing described in the presented work has allowed us to determine LAB that might be responsible for the production of bacteriocins which were linked to the inhibition of foodborne pathogenic bacteria in our previously published study [ 19 ]. Lenti.…”

“…Kefir K, on the other hand, appears to be the most unique kefir in terms of its species-level taxonomy and its composition comprised of LAB reported to produce bacteriocins. In our former work [ 19 ], kefir K exhibited antimicrobial activity against a diverse group of foodborne pathogenic indicators. Due to kefir K’s robust antimicrobial activity and its unique species-level taxonomy, our goal is to carry out additional research on kefir K with emphasis on isolation and characterization of LAB and their bacteriocins as well as application of these bacteriocins as natural, clean-label biopreservatives for shelf life protection and assurance of microbial food safety.…”

“…In our recently published work [ 19 ], the antimicrobial activities of artisanal kefir products from Fusion Tea, Britain, the Caucuses region, Ireland, Lithuania, and South Korea were investigated against select foodborne pathogens. It was confirmed that bacteriocin production is the main reason for these kefirs’ antimicrobial activity [ 19 ]. In the presented work, the 16S rRNA gene sequencing was used to reveal bacterial populations and elucidate the diversity and abundance of LAB species in these international artisanal kefirs.…”