Inhibition of Methicillin Resistant Staphylococcus aureus Biofilm by Ethanol Extracts of Sauropus androgynus and Solanum torvum

Abstract

Sauropus androgynus and Solanum torvum are known to possess antioxidant, anti-cancerous, anti-fungal and antiseptic properties. The current study aimed to evaluate the effect of ethanol extracts of Sauropus androgynus leaves and Solanum torvum fruit in prevention of biofilm formation by methicillin resistant Staphylococcus aureus. The study also assessed the presence of bioactive compounds and their ability to modify the cell surface hydrophobicity of methicillin resistant Staphylococcus aureus biofilm. In this study, methicillin resistant Staphylococcus aureus isolates obtained from tertiary care hospitals in Coimbatore were subjected to antibiotic susceptibility testing and biofilm formation. Among the 20 methicillin resistant Staphylococcus aureus isolates, all were found to be 100 % sensitive to vancomycin and 100 % resistant to cotrimoxazole and tetracycline. Two methicillin resistant Staphylococcus aureus isolates were observed to be strong biofilm producers confirmed by microtiter plate method and only one methicillin resistant Staphylococcus aureus isolate was used for further studies. Phytochemical screening of plant materials was carried out to identify the bioactive compounds potentially responsible for the biological properties. Among the plant extracts tested, extracts of Sauropus androgynus leaves showed a maximum zone of inhibition (18 mm), whereas the zone of inhibition exhibited by Solanum torvum fruit extracts was 16 mm at 200 µg/ml against methicillin resistant Staphylococcus aureus. Minimum inhibitory concentration and minimum biofilm inhibitory concentration testing of extracts of Sauropus androgynus leaves and Solanum torvum fruit were also carried out against methicillin resistant Staphylococcus aureus, in which each extract at a concentration of 5 mg/ml was found to inhibit methicillin resistant Staphylococcus aureus growth and biofilm formation via the microtiter plate method. Moreover, there was an increase in cell surface hydrophobicity of methicillin resistant Staphylococcus aureus biofilm from 33.96 to 61.90 % at 150 µg/ml of extracts of Sauropus androgynus leaves, while Solanum torvum fruit extracts showed 46.80 % hydrophobicity. Similarly, anti-adhesive activity was found to be higher in extracts of Sauropus androgynus leaves (0.008) when compared to Solanum torvum fruit extracts (0.016) at 50 µg/ml. The current study reports for the first time the efficacy of Sauropus androgynus and Solanum torvum extracts as a promising source of anti-biofilm agents, especially against methicillin resistant Staphylococcus aureus.