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

Abstract

Many studies have linked the antimicrobial properties of kefir with the presence of bacteriocins and organic acids. In the present work, results obtained from bacteriostatic and bactericidal studies, and from RP-HPLC, Mass Spectrometry and proton NMR analysis, show that a sample of milk kefir grains is able to produce an antimicrobial fraction, denoted FK-1000, composed of sugars and amino acids, predominantly polymers of alanine, doublets of tyrosine and phenylalanine. Since this fraction is a lyophilized product whose molecular profile is different from bacteriocins and simple carboxylic acids, its antimicrobial effect cannot be attributed to these molecules, or to alcohols or hydrogen peroxide. The fraction is bactericidal against weak-acid-resistant MRSA and weak-acid resistant P. aeruginosa at pH 5, and is bacteriostatic against both pathogens at pH 7. In combination formulation, the FK-1000 fraction is able to increase fivefold the effect of streptomycin against P. aeruginosa and it is not toxic to human epithelial cells at antimicrobial concentrations. 16 S rRNA microbiota analysis of antimicrobial-producing and non-producing kefir grains demonstrated that they are distinct. In summary, the results indicate that milk kefir grains can produce different classes of molecules with potent antibiotic activity against resistant bacteria.

Bioactive Compounds from Kefir and Their Potential Benefits on Health: A Systematic Review and Meta-Analysis

“…Some microorganisms in kefir produced fractions with antimicrobial activity against Clostridium difficile , Pseudomonas putida , Pseudomonas aeruginosa , and methicillin-resistant Staphylococcus aureus [ 59 , 62 , 63 ]. FK-1000 at 25 mg/mL inhibited the growth of Pseudomonas aeruginosa by 91%.…”

“…It demonstrates the potential of FK-1000 for use in combination therapy. Another important aspect is that a 50 mg/mL concentration of FK-1000 was not toxic to human epithelial cells, increasing the relevance of this compound's use as a treatment [ 62 ].…”

Invited review: Milk kefir microbiota—Direct and indirect antimicrobial effects

“…Recently, the antimicrobial fraction (FK-1000) composed of sugars and amino acids obtained from kefir serum showed bactericidal effects against Ps. aeruginosa ATCC-27853 and methicillin-resistant Staphylococcus aureus (Marques et al, 2020). Also, Purutoğlu et al (2020) demonstrated that L. kefiranofaciens KF16 and L. lactis KF48 isolated from kefir grains showed the highest inhibitory effects against Staphylococcus aureus ATCC 25923, Y. enterocolitica ATCC 27729, B. cereus BC6830, E. coli BC1402, and Salmonella typhimurium RSSK95091.…”

Antibacterial Mechanism of Dellaglioa algida against Pseudomonas fluorescens and Pseudomonas fragi

“…From Section 3.1, there exists a special acidoid, protein, or small peptide in D. algida which can inhibit the target psychrotrophic Pseudomonas, i.e., P. fragi and P. fluorescens, and it is sensitive to protease and temperature. Since the antibacterial effects are achieved by organic acid (lactic acid and acetic acid) [32], bacteriocin [40], or novel antibacterial molecules [41] that are different from any carboxylic acid in the existing studies about the investigation of inhibition mechanism of other Lactobacillus on Pseudomonas, it can be reasonably regarded that the antibacterial substance is one/some novel bacteriocin or organic acid. It is worth noting that, in this paper, the diameters of the inhibition zones of D. algida on P. fragi and P. fluorescens are 21.36 mm and 33.75 mm, respectively.…”