Evaluation of anti-biofilm activity of Lactobacillus rhamnosus GG and Nisin on the expression of aap, ica-A and ica-D as biofilm-associated genes of Staphylococcus epidermidis

Background and Objectives: In the present study, the anti-biofilm activity of Lactobacillus rhamnosus GG and Nisin was investigated on biofilm-forming abilities of Staphylococcus epidermidis strains and the expression of the biofilm-associated genes. Materials and Methods: In this study, the standard strain of L. rhamnosus GG (ATCC 53103) and Nisin were used to assess their anti-microbial and anti-biofilm effects on S. epidermidis (RP62A). Results: The MIC and MBC analysis showed that Nisin at 256 μg/mL and 512 μg/mL, and L. rhamnosus GG at 1×107 CFU/ mL and 1×108 CFU/mL have anti-microbial activity compared to the negative control respectively. L. rhamnosus GG bacteria and Nisin inhibited the biofilm formation of S. epidermidis based on optical density of at 570 nm (P 0.001). The relative mRNA expression of aap, icaA, and icaD genes was significantly reduced compared to the negative control after treating S. epidermidis with sub-MIC of Nisin (0.44, 0.25 and 0.6 fold, respectively) (P 0.05). In addition, the relative expression of aap and icaA genes, but not icaD (P 0.05), was significantly lower than the negative control (0.62 and 0.7 fold, respectively) (P 0.05), after exposure to the sub MIC of L. rhamnosus GG. Conclusion: Nisin and L. rhamnosus GG exhibit potent activity against biofilm-forming abilities of S. epidermidis and these agents could be utilized as an anti-biofilm agents against S. epidermidis infections. .