eng Oriental Scientific Publishing Company Biosciences Biotechnology Research Asia 0973-1245 2016-05-06 8 1 353 355 9407 article R. P. Maruthamalai Rasi 1 Thilagavathy Daniel 1 Department of Biology, Gandhigram Rural Institute - Deemed University, Gandhigram - 624 302 (India). Petroleum ether extract of the leaves of plants such as Acalypha indica, Achyranthes aspera, Aegle marmelos, Andrographis paniculata and Leucas aspera were screened for antibacterial activity against three selected bacteriae i.e Escherichia coli, Staphylococcus aureus and Proteus spp. The mixed plant extracts were also screened for synergistic effect against the three selected bacteriae. Among the five individual plants tested a higher degree of antibacterial effect was exhibited by the leaves of A. marmelos, L. aspera, and A. paniculata. E.coli was susceptible to the extracts of all the five individual plants. The zone of inhibition was higher when the plates were incubated for 48h than for 24h. Among the mixtures of extracts tested, higher synergistic efficacy was observed in the mixtures of A. marmelos + A. paniculata, A. marmelos + L. aspera and A. marmelos + A. indica at 24h and 48h against E.coli. https://www.biotech-asia.org/vol8no1/a-study-on-the-antibacterial-activity-of-certain-plant-extracts/ Plant extracts; Antibacterial activity; Escherichia coli and Synergistic efficacy