Modulatory Effect of Oyster Culinary-Medicinal Mushroom Pleurotus ostreatus (Agaricomycetes) Extract on uspA Gene Expression and Antibiotic Susceptibility of Staphylococcus aureus Exposed to Antibiotic Stress

Mushrooms have been found to be one of the main sources of nutrients to man, but their nutraceutical approach to life science is still being studied. The proposed concept that mushrooms serve both as food and medicine has placed mushrooms as nutraceuticals. Mushrooms have been discovered to be a good source of a variety of nutritional bioactive compounds with numerous health benefits as well as medicinal properties. The aim of this research was to evaluate the modulatory effect of Pleurotus ostreatus extract on Staphylococcus aureus uspA+ gene expression and antibiotic susceptibility. In this study, indigenous P. ostreatus mushroom extract used was screened for its bioactive phytochemical contents. The effect of P. ostreatus extract on uspA+ S. aureus gene expression and antibiotic susceptibility was conducted using reverse transcriptase polymerase chain reaction (RT-PCR) technique and the Kirby-Bauer test method, respectively. Results obtained showed that uspA genes were domicile in S. aureus and were expressed when exposed to sublethal antibiotic concentrations, whereas the presence of P. ostreatus extract inhibit uspA+ S. aureus gene expression. The susceptibility results showed that inhibition zone diameters (IZDs) were found to be in the ranges between 0- and 8-mm diameter for unexposed S. aureus uspA+ genes to mushroom extract, whereas the IZDs increased to about 15 to 20 mm diameter when exposed to mushroom extract. The mushroom bioactive compounds quantitative analysis showed high flavonoid (63.4 ± 3.6 mg/dL), tannins (29.27 ± 1.0 mg/dL) and phenols (22.0 ± 2.7 mg/dL). Based on these research findings, it shows that P. ostreatus extract can serve as a modulating agent that can be used to regulate the expression of uspA+ gene in S. aureus and can optimize the susceptibility enhancement in antibiotic-mediated S. aureus.