Background: Staphylococcus aureus is a superbug which is infamous for causing wound infections. Unfortunately it is developing resistance quickly against commonly used antibiotics. Antimicrobial drugs effective against methicillin resistant staphylococcus aureus are too expensive to afford by impoverish population in our country. However, herbal medicines are seen to be equally effective with less severe adverse effects. There is need to explore alternative medicines of botanical origin to cure dangerous bacteria. Oenothera biennis contains phytochemicals which have antimicrobial activity against some gram negative and gram positive microorganisms.

Objectives: To evaluate the minimum inhibitory concentration of Oenothera biennis seed extract against staphylococcus aureus by using different concentrations.

Study Design: In Vitro antibacterial study.

Settings: The study was conducted in microbiology laboratory of Shaikh Zayed Medical Complex, Lahore.

Duration: One year.

Methodology: Oenothera biennis extract was prepared in 95% Ethanol in biochemistry laboratory of Pakistan Council of Scientific and Industrial Research (PCSIR) Lahore. Staphylococcus aureus isolates were procured from microbiology laboratory and American Type Culture Collection (ATCC) strains used as quality control for MSSA & MRSA, were purchased from musaji adam and sons Karachi (imports@science-ware.com). The antibacterial activity of oenothera biennis seed extract against staphylococcus aureus was tested by deep well broth microdilution and disc diffusion method. Different concentrations of stock solutions (100µg/10µl to 500µg/10µl of DMSO) were used to test antimicrobial effect to establish dose response relationship.

Results: Results were measured and compared according to Clinical and Laboratory Standard Institute. Oenothera biennis seed extract inhibited growth of methicillin sensitive and methicillin resistant staphylococcus aureus isolate from laboratory as well as ATCC strains with minimum inhibitory concentration 530µg/10µl solvent. Whereas other concentrations 50 µg/10µl ,100 µg/10µl ,150 µg/10µl ,200 µg/10µl ,250 µg/10µl ,300 µg/10µl ,350 µg/10µl ,400 µg/10µl ,450 µg/10µl  and 500 µg/10µl had no effect at all.

Conclusion: Oenothera biennis extract inhibits growth of staphylococcus aureus at concentration of 530µg remarkably. This can inhibit both MSSA & MRSA already proved in our study. This could be beneficial as an alternate medicine. However, further research is needed to be conducted for animal study.

Key words: Oenothera biennis, ethanolic extract, Methicillin sensitive, Methicillin Resistant Staphylococcus aureus, MSSA, MRSA.