Employment of Spore-Forming Probiotics to Combat Persister Cells of Staphylococcus Epidermidis.

Background: In this study, spore-forming probiotics were employed to eradicate Staphylococcus epidermidis biofilms and the presence and expression of genes involved in stress response was examined.

Methods: Polymerase chain reaction (PCR) assay was used to detect rpoS, relA and mazF genes in S. epidermidis ATCC 12228. Biofilm production was investigated by microtiter plate (MTP) assay. 100X minimum inhibitory concentration (MIC) of gentamycin was used to induce persister cells in planktonic and biofilm bacterial cells. The expression of rpoS, relA, and mazF genes was assessed at different time intervals of 2, 8, and 24 h using real-time PCR assay. Then, dilutions of 1, 0.5, and 0.25 µg/ml of the supernatant of Bacillus coagulans culture was used to eradicate the persister cells and the number of colonies was determined.

Results: Persister cells of S. epidermidis were formed after 7 h in planktonic and 5 h in the biofilm structure after exposure to 50 µg/ml of gentamycin. The expression of mazF and rpoS in biofilm structure and the expression of rpoS and relA in persister cells were significantly higher compared to the control (p< 0.05). The number of persister cells showed a reduction of log 2.4 and log 0.8 after exposure to 1 and 0.5 µg/ml B. coagulans supernatant, respectively, but no reduction was observed at the concentration of 0.25 µg/ml.

Conclusion: The results showed that the supernatant of probiotics containing their secretive metabolites can be used as a novel approach to combat persister cells.