Lactobacillus rhamnosus GG Inhibits the Toxic Effects of Staphylococcus aureus on Epidermal Keratinocytes

Abstract

ABSTRACTFew studies have evaluated the potential benefits of the topical application of probiotic bacteria or material derived from them. We have investigated whether a probiotic bacterium,Lactobacillus rhamnosusGG, can inhibitStaphylococcus aureusinfection of human primary keratinocytes in culture. When primary human keratinocytes were exposed toS. aureus, only 25% of the keratinocytes remained viable following 24 h of incubation. However, in the presence of 108CFU/ml of liveL. rhamnosusGG, the viability of the infected keratinocytes increased to 57% (P= 0.01).L. rhamnosusGG lysates and spent culture fluid also provided significant protection to keratinocytes, with 65% (P= 0.006) and 57% (P= 0.01) of cells, respectively, being viable following 24 h of incubation. Keratinocyte survival was significantly enhanced regardless of whether the probiotic was applied in the viable form or as cell lysates 2 h before or simultaneously with (P= 0.005) or 12 h after (P= 0.01)S. aureusinfection. However, spent culture fluid was protective only if added before or simultaneously withS. aureus. With respect to mechanism, bothL. rhamnosusGG lysate and spent culture fluid apparently inhibited adherence ofS. aureusto keratinocytes by competitive exclusion, but only viable bacteria or the lysate could displaceS. aureus(P= 0.04 and 0.01, respectively). Furthermore, growth ofS. aureuswas inhibited by either live bacteria or lysate but not spent culture fluid. Together, these data suggest at least two separate activities involved in the protective effects ofL. rhamnosusGG againstS. aureus, growth inhibition and reduction of bacterial adhesion.