Antibiofilm and antibacterial activities of swietenia macrophylla methanolic extract (SMME) against gram-positive bacteria / Siti Sarah Diyana Amran

Gram-positive bacteria are responsible for 62% - 76% of all bloodstream infections in human. They can cause infections such as skin infections, pneumonia, sinusitis and anthrax. Some of these bacteria are able to form biofilm, causing serious impact in health as biofilm is known to be difficult to eradicate as they are more resistant to kill when treated with antibiotics. Swietenia macrophylla is a medicinal plant that had been used by folks to treat some diseases like fever and diarrhoea could be an excellent source drug to fight off this problem. The objectives of this research were to investigate phytochemical profile, antibacterial activity and antibiofilm activity of Swietenia macrophylla methanol extract (SMME). The phytochemical profile was analysed by Gas Chromatography Mass Spectrometry (GC-MS). The antibacterial and antibiofilm activities of SMME were assessed against four Gram-positive bacteria namely Staphylococcus aureus ATCC 33862, Streptococcus pneumonia ATCC 19615, Bacillus cereus ATCC 11778 and Clostridium sporogenes ATCC 13124 by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) and biofilm assay respectively. Time kill assay was performed to further investigate the antibiofilm activity of selected test concentration against the microorganisms. Phytochemical screening revealed the presence of six compounds in the SMME. The major compound was -amyrin (22.8%). SMME showed the lowest minimum inihibititory concentration (MIC) values against B. cereus (31.25 µg/ml) and C. sporogenes (31.25 µg/ml) and the lowest minimum bactericidal concentration (MBC) value against S. aureus (1000 µg/ml). Meanwhile, the SMME significantly (p< 0.05) inhibited all the biofilms. It promoted the biofilm inhibition formation during early hours and started to inhibit after twelve hours. Biofilm inhibitory concentration (BIC50)revealed B. cereus exhibited the highest activity. The present study confirmed the efficacy of SMME as antibacterial agent and suggested the possibility of employing SMME in drug for the treatment of infectious diseases caused by the tested bacteria. In conclusion, the bioactive compounds which are present in SMME may play an important roles in antibacterial and antibiofilm activity against Gram-positive bacteria.