Objective: Increasing emergence of antibiotic resistance has led to developing alternative methods to overcome this issue. The antibiotic resistance is mainly associated with formation of biofilms. Restoring healthy microbiota is one of these methods to fight the biofilm formation. In terms of this, the use of probiotics is a novel approach. In this study, we aimed at investigating the effect of exopolysaccharides (EPSs) of different lactic acid bacteria as probiotics on Bacillus spp isolated from the ocular surface, which is known to form biofilms.
Materials and methods: Pathogenic microorganisms were cultivated in "Brain-Hearth infusion" (BHI) broth, and lactic acid bacteria were grown in "De Man, Rogosa, Sharpe" and M17 broth. Molecular identification of lactic acid bacteria was made according to the sequence information of the 16S rRNA gene region. Antimicrobial activity of lactic acid bacteria was determined by sandwich overlay method. The minimum inhibitory concentration values of the exopolysaccharides and antibiofilm activity were determined by microtitration method. For evaluating the effect of EPSs of probiotic bacteria on biofilm, the mean and standard deviations of optical density values were calculated.
Results: The most effective EPS against B. cereus was EPS from L. rhamnosus 24, followed by EPS from L. plantarum and L. acidophilus. The biofilm formation of all pathogenic bacteria that were exposed to probiotic bacteria except L. rhamnosus 621 and 622 and L. rhamnosus 3111 was lower than the biofilm formation of the control group.
Conclusions: EPSs obtained from lactic acid bacteria have antibacterial and antibiofilm activity on pathogenic bacteria isolated from ocular surface. This study is one of the pioneer studies in restoring healthy microbiota on ocular surface with the anticipated forthcoming use of topical probiotics.