Evaluation of the presence and time-variable expression levels of rpoS, relA and mazf genes during biofilm formation in Staphylococcus epidermidis

Background and purpose:Staphylococcus epidermidis is an opportunistic pathogen that is involved in the development of infections associated with the use of implants and medical devices. Biofilm formation is one of the most important virulence factors of this microorganism, which vastly depends on various factors, including different proteins. In the present study, the expression levels of three proteins including RpoS, RelA and MazF at different time intervals during the course of biofilm formationin Staphylococcus epidermidis were investigated. Materials and Methods: In the present case-control study PCR assay was used to detect rpoS, relA and mazF genes in Staphylococcus epidermidis ATCC 12228. Biofilm production was investigated by microtiter plate (MTP) method. Real-time PCR was used to determine the expression levels of studied genes after 2, 8, and 24 h during the course of biofilm formation. Data were analyzed using GraphPad Prism 8 statistical software (GraphPad Software, Inc.). One-way analysis of variance was used to evaluate the mean expression changes of the studied genes and P-value <0.05 was considered significant. Results:Staphylococcus epidermidis contained all the studied genes and had a strong biofilm formation power. The studied genes showed different expression levels at different time intervals during biofilm formation by real-time PCR method. Expression levels of rpoS gene were the highest at 24 h (6.7 ± 0.252) (p<0.001), whereas mazF gene showed the highest expression level at 8 h (6 ± 0.208) (p<0.001) during the course of biofilm formation. In addition, the expression level of relA gene peaked at 2h (3.9 ± 0.361) (p<0.001) and then progressively decreased at 8 (1.7 ± 0.265) and 24h (1.2 ± 0.153) (p<0.05). The results of the comparison of rpoS gene expression changes compared to relA gene (2.667 ± 1.175) and also mazF gene (0.2333 ± 1.175) using Dunnett's multiple comparisons test was not significant (p˃0.05). Conclusion: Our results suggest the importance of RpoS, RelA and MazF proteins in the establishment and development of the biofilm structure in the studied strain. In addition, our results showed the important role of RpoS protein during biofilm formation, and the importance of RelA protein at the beginning of biofilm formation stages.