The last decade witnessed the emergence of Staphylococcus aureus- a versatile human pathogen, as a deadly superbug. The enormous genetic plasticity of the organism assists it to endlessly evolve resistance mechanisms against existing anti-infectives thus necessitating the need to control the spread of resistant staphylococcal isolates in hospitals and health care settings. This in turn demands the incessant exploration of newer biological matrices in search of diverse chemical entities with novel drug targets. Since time immemorial higher plants continue to be the best source of newer compounds with high therapeutic potential. Lead fractions from same or different plants can be developed into effective antibacterial polyherbal formulations. A lead fraction from methanolic extract of leaves of Callistemon rigidus exhibited a dose dependent antistaphylococcal activity during in vitro agar well assay against a panel of twenty seven clinical multidrug resistant S. aureus isolates. Further, minimal inhibitory concentration (MIC) evaluation by in vitro 96-well microplate based assay established a MIC range of 1.25–80 μg/ml as compared to 5–320 μg/ml of positive control, Cefuroxime sodium. The MIC50 and MIC90 of the methanolic lead fraction were 5 μg/ml and 40 μg/ml respectively. The present study thus signifies the vast potential of the lead fraction from Callistemon rigidus for future development into a herbal drug/ formulation and to impede global health crisis due to multidrug resistant Staphylococcus aureus.
 H. Watanabe, L. Masaki, N. Asoh, K. Watanabe, K. Oishi, S. Kobayashi, A. Sato and T. Nagataka: “Molecular analysis of Methicillin resistant Staphylococcus aureus as a causative agent of Bronchopulmonary infection: relation to colonization in upper respiratory tract”, J. Clin. Microbiol., Vol. 38, (2000), pp. 3867–3869.
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