Antimicrobial and healing activity of kefir and kefiran extract

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Abstract

Kefir and its insoluble polysaccharide, kefiran, were both tested for antimicrobial and cicatrizing activities against several bacterial species and Candida albicans using an agar diffusion method. Comparator antimicrobials were also tested. Cicatrizing experiments were carried out on Wistar rats with induced skin lesions and Staphylococcus aureus inoculation, using a topical application of a 70% kefir gel. Both kefir and kefiran showed some activity against all organisms tested; the highest activity was against Streptococcus pyogenes. Cicatrizing experiments using 70% kefir gel had a protective effect on skin connective tissue and 7 days treatment enhanced wound healing compared with 5 mg/kg of neomycin–clostebol emulsion.

Introduction

Nosocomial bacteraemia associated with resistant organisms and postoperative surgical infections is a serious problem [1]. Since antibiotic use became widespread 50 years ago, bacteria have relentlessly developed resistance [2]. Because of this, efforts have been made to develop and study new compounds outside conventional antibiotic therapy [2]. These include new organic compounds [3], peptides isolated from vertebrates [4], honey preparations [5], ozonized oils [6] and probiotic strains [7]. A probiotic may be a single strain or a mixture of different organisms and are claimed to enhance wellbeing through immunomodulatory, metabolic and barrier activities against pathological processes. Kefir is an example of a probiotic mixture of bacteria and yeasts [8].

Kefir is a microbial symbiont mixture that produces jelly-like grains as it grows, that contain both lactic acid bacteria (Lactobacillus, Lactococcus, Leuconostoc, Acetobacter and Streptococcus spp.) and yeasts (Kluyveromyces, Torula, Candida and Saccharomyces spp.). Both bacteria and yeasts are surrounded by a polysaccharide matrix, named kefiran, a water-soluble branched glucogalactan, which has been reported to have antibacterial, antimycotic and antitumour activity [9]. Kefir is claimed to act against the pathogenic genera Salmonella, Helicobacter, Shigella and Staphylococcus, and Escherichia coli and to have some anti-inflammatory activities [10]. These two properties of kefir might be of use as an alternative treatment for patients infected with a single or multi-resistant strains of organisms.

This study, therefore, looked at the antimicrobial and cicatrizing activities of kefir and kefiran using agar diffusion experiments and cicatrizing tests on rats.

Section snippets

Microorganisms used

The microorganisms used were Staphylococcus aureus ATCC 6538, Streptococcus salivarius ATCC 39562, Streptococcus pyogenes ATCC 17568, Pseudomonas aeruginosa ATCC 27853, Candida albicans ATCC 10232, Salmonella typhimurium ATCC 14028, Listeria monocytogenes ATCC 4957 and E. coli ATCC 8739. All strains were kept frozen in liquid nitrogen and cultured on appropriate media following the standard guidelines of NCCLS [11].

Kefir

Starter grains (5 g) kept at Lab. Fitofarmacos (Unifenas, MG, Brazil) were

Susceptibility tests

Inhibition ratios of kefiran against the pathogenic strains were determined from minimum least squares applied to diameter values at 5, 20 and 50 μg. The results showed S. pyogenes to be the most sensitive microorganism to kefiran, followed by S. aureus and S. salivarius. S. typhimurium, C. albicans and L. monocytogenes were less sensitive to kefiran and P. aeruginosa and E. coli the least sensitive. Minimal MIC and MBC values for kefiran against all strains tested ranged from 462 (MIC) to 494 

Discussion

The benefits of probiotic microorganisms have been tested in double-blind and placebo-controlled studies of cancer, carcinogen formation, reduction of serum cholesterol, stimulation of immune system and prevention or treatment of human infections [13]. Fermented suspensions of kefir grains are claimed to have clinical effects on diarrhoeal disease, urinary tract infection, salmonella, streptococcal and Helicobacter pylori infections [10], [14]. Although antimicrobial activity by several

Acknowledgements

This work was supported by National Council of Research and Technology Development—CNPq, Research Support Foundation of Minas Gerais—FAPEMIG, and University of Alfenas (Unifenas).

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