10.22376/ijpbs.2019.10.1.p1-12 Volume 5 Issue 1 2014 (January - March) The antibacterial activity of crude and essential oil extract of rosemary ( lessThan i greaterThan Rosmarinus officinalis lessThan /i greaterThan L.) against the infectious bacteria viz., lessThan i greaterThan Escherichia coli, Bacillus subtilis, Pseudomonas lessThan /i greaterThan spp and lessThan i greaterThan Staphylococcus aureus lessThan /i greaterThan were evaluated lessThan i greaterThan in vitro lessThan /i greaterThan . It was found that rosemary oil exhibits high antibacterial activity against lessThan i greaterThan E. coli, B.subtilis, S.aureus, lessThan /i greaterThan and lessThan i greaterThan Pseudomonas lessThan /i greaterThan spp, when compared to crude extract. The lessThan i greaterThan in vitro lessThan /i greaterThan Minimum Inhibitory Concentration (MIC) of rosemary oil was found to be 100μg ml lessThan sup greaterThan -1 lessThan /sup greaterThan for inhibiting the growth of lessThan i greaterThan Pseudomonas lessThan /i greaterThan spp; 50μg ml lessThan sup greaterThan -1 lessThan /sup greaterThan for inhibiting the growth of lessThan i greaterThan B. subtilis lessThan /i greaterThan and lessThan i greaterThan S. aureus lessThan /i greaterThan whereas, it was found to be 12.5μg ml lessThan sup greaterThan -1 lessThan /sup greaterThan for lessThan i greaterThan E. coli. lessThan /i greaterThan The statistical analysis for MIC of lessThan i greaterThan R. officinalis lessThan /i greaterThan oil was found to be 42.82µg/ml for inhibiting the growth of lessThan i greaterThan B.subtilis lessThan /i greaterThan and lessThan i greaterThan S. aureus lessThan /i greaterThan , it was found to be 10.88µg/ml for lessThan i greaterThan E.coli lessThan /i greaterThan and 85.66µg/ml for lessThan i greaterThan Pseudomonas lessThan /i greaterThan spp GAYATRI M.C , SUDHA U, SHUBHA J AND SURESH R Antibacterial activity, Bacillus subtilis, Essential oil, Escherichia coli, Rosmarinus officinalis, Pseudomonas spp, Staphylococcus aureus 654-662