Antimicrobial Activity of Kefir against Various Food Pathogens and Spoilage Bacteria

Abstract

Kefir is a unique fermented dairy product produced by a mixture of lactic acid bacteria, acetic acid bacteria, and yeast. Here, we compared the antimicrobial spectra of four types of kefirs (A, L, M, and S) fermented for 24, 36, 48, or 72 h against eight food-borne pathogens. Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, Enterococcus faecalis, Escherichia coli, Salmonella Enteritidis, Pseudomonas aeruginosa, and Cronobacter sakazakii were used as test strains, and antibacterial activity was investigated by the spot on lawn method. The spectra, potencies, and onsets of activity varied according to the type of kefir and the fermentation time. The broadest and strongest antimicrobial spectrum was obtained after at least 36-48 h of fermentation for all kefirs, although the traditional fermentation method of kefir is for 18-24 h at 25°C. For kefir A, B. cereus, E. coli, S. Enteritidis, P. aeruginosa, and C. sakazakii were inhibited, while B. cereus, S. aureus, E. coli, S. Enteritidis, P. aeruginosa, and C. sakazakii were inhibited to different extents by kefirs L, M, and S. Remarkably, S. aureus, S. Enteritidis, and C. sakazakii were only inhibited by kefirs L, M, and S, and L. monocytogenes by kefir M after fermentation for specific times, suggesting that the antimicrobial activity is attributable not only to a low pH but also to antimicrobial substances secreted during the fermentation.

A new class of antimicrobial molecules derived from kefir, effective against Pseudomonas aeruginosa and methicillin resistant Staphylococcus aureus (MRSA) strains

“…This is an important result to note, since antimicrobial molecules often react differently at different pHs 30,31 . Thus, the power of kefir serum to kill bacteria is attributable not to a low pH but to antimicrobial molecules produced during fermentation, in corroboration with other studies that demonstrated that the antimicrobial activity of four different samples of kefir was not related to their low pH (between 3.65 and 4) 3 .…”

Antimicrobial and anti-biofilm activities of Lactobacillus kefiranofaciens DD2 against oral pathogens

“…The antimicrobial activity of kefir or its constituent microorganisms against various foodborne pathogens and spoilage bacteria has been reported previously [2,27]; however, the actual antimicrobial properties against cariogenic bacteria have not previously been demonstrated. LAB produce various antimicrobial compounds such as organic acids, hydrogen peroxide, diacetyl, and bactericidal polysaccharides or peptides [28].…”

Colostrum-derived bioactive peptides obtained by fermentation with kefir grains enriched with selected yeasts

“…These compounds could be implicated in the reduction of food borne pathogens and also in the treatment and prevention of gastroenteritis and vaginal infections (Leite et al, 2013). The antimicrobial activity of four kefirs types, fermented for 24-72 h against eight food-borne pathogens (Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, Enterococcus faecalis, Escherichia coli, Salmonella enteritidis, Pseudomonas aeruginosa and Cronobacter sakazakii) was revealed by spot method (Kim et al, 2016). The strongest antimicrobial spectrum was obtained after at least 36-48 h of fermentation for all kefirs.…”