Prophylactic efficacy of probiotics and their metabolites against Staphylococcus epidermidis.

Background: Staphylococcus epidermidis is a prevalent common microorganism found on the skin of most mammals, including humans. However, S. epidermidis is also known as an opportunistic pathogen that can cause diseases if the skin microbiome becomes skewed to favor its overgrowth. This situation can be worsened if the causative strains are antibiotic-resistant. To explore potential alternatives to replace conventional antibiotics, we aim to use probiotics, specifically Lacticaseibacillus rhamnosus and Lactiplantibacillus plantarum, in controlling the growth, colonization, and biofilm formation of a multidrug-resistant S. epidermidis.

Results: Multidrug-resistant S. epidermidis was co-cultured with either L. rhamnosus or L. plantarum, and antimicrobial activity was assessed by counting S. epidermidis colonies at various timepoints. Under co-culture conditions, growth of S. epidermidis was decreased over time in the presence of either probiotic, specifically, a significant reduction was observed after 48 hours (p=0.0062). Additionally, S. epidermidis was treated with cell-free culture supernatant (CFCS) collected from probiotics to investigate the mechanism of inhibition. CFCS from 72-hour Lactobacilli cultures significantly inhibited S. epidermidis growth within 4 hours (p<0.05), and no S. epidermidis was detected after 72 hours (p=0.0003) when treated with 50% CFCS. Both CFCSs also reduced biofilm formation and bacterial counts after 24 hours, with complete inhibition by 48 h. Gene expression analysis revealed that exposure to CFCS led to downregulation of S. epidermidis genes associated with metabolism and cell division (arcC, gts, mutS, mur1, and ftsZ). Fluorescence microscopy indicated compromised cell wall integrity, evidenced by reduced HADA fluorescence and increased propidium iodide staining.

Conclusion: L. plantarum and L. rhamnosus possess strong antimicrobial activity against multidrug-resistantS. epidermidis, supporting their potential as alternative strategies to control S. epidermidis colonization.