A qualitative investigation of the antimicrobial potential oftwo lactic acid bacteria supernatant against prevalent skin pathogenicbacteria

Background and Aim : Skin is the human body's largest organ. It plays a vital role as the primaryprotective barrier of the body against pathogens [۱]. An open wound becomes a suitable place fora wide range of microorganisms [۲]. Probiotics are bacteria or yeast that confer a health benefit onthe host and may have a role in preventing and treating nonhealing wounds by modulating hostmicrobeinteractions. The most commonly used probiotics are species of lactic acid bacteria (LAB)[۳,۴]. In this work, we examined the ability of the supernatant of two strains of potentially probioticlactic acid bacteria (Lactobacillus casei PTCC۱۶۰۸ and Lactobacillus acidophilus PTCC۱۶۴۳)against four of the most common primary skin pathogens including Staphylococcus aureusATCC۲۵۹۲۳(Sa), methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosaATCC۲۷۸۵۳(Pa), and Pseudomonas aeruginosa PAO۱.Methods : The above Lactobacillus strains were activated for ۲۴ h in MRS broth (Ibresco, Iran)at ۳۷◦C in anaerobic conditions. The pH of the supernatants was measured (Table۱). Afterfiltration(۰.۲۲ mm pore size; Millipore), three concentrations of lyophilized supernatant (۲۵mg/ml,۵۰ mg/ml and ۷۵ mg/ml) were prepared using sterile distilled water as a solvent. The antimicrobialactivity of supernatants was measured using agar-well diffusion [۵]. The above test was alsoperformed using neutralized supernatants of Lactobacillus strains with ۸ M sodium hydroxide.Results : According to the presented data, the diameter of the growth inhibition zone of pathogenswas enlarged by increasing the concentration of the supernatants. The highest diameter of theinhibition zone (۱۴.۶±۰.۵ mm) against Pseudomonas aeruginosa was recorded with Lactobacilluscasei PTCC۱۶۰۸ supernatant. No inhibition zone was observed in presence of neutralizedsupernatants of Lactobacillus strains.Conclusion : A comparison of the inhibition zone produced by Lactobacillus strains supernatantsuggests that Lactobacillus casei has more effective antimicrobial activity than Lactobacillusacidophilus. Besides, it was shown neutralization of supernatant of both Lactobacillus strainseliminates the antibacterial property. It seems that the antimicrobial effect of the supernatants isrelated to the acidic content, which needs more detailed investigations.

کلیدواژه ها:

Agar-well diffusion ، bacterial pathogens ، skin ، supernatant ، wound