10.22376/ijpbs.2019.10.1.p1-12 Volume 5 Issue 1 2014 (January - March) Ethanol and hexane extracts of twenty Thai medicinal plants, used in Thai traditional medicine for the treatment of infectious and septic diseases, were screened lessThan i greaterThan in vitro lessThan /i greaterThan for antibacterial activity against lessThan i greaterThan Bacillus cereus, lessThan /i greaterThan lessThan i greaterThan Escherichia coli lessThan /i greaterThan and lessThan i greaterThan Staphylococcus aureus, lessThan /i greaterThan using disc diffusion method. The ethanol extracts of lessThan i greaterThan Clerodendrum lessThan /i greaterThan lessThan i greaterThan inerme lessThan /i greaterThan (L.) Gaertn., lessThan i greaterThan Combretum qurdrangulare lessThan /i greaterThan L., lessThan i greaterThan Psidium guajava lessThan /i greaterThan Kurz., and lessThan i greaterThan Stephania lessThan /i greaterThan lessThan i greaterThan venosa lessThan /i greaterThan (Blume) Spreng. showed antibacterial activity against all three tested pathogens. Based on minimum inhibitory concentration (MIC) of these four medicinal plant extracts, the ethanol extract of lessThan i greaterThan C. inerme lessThan /i greaterThan demonstrated the highest antibacterial potency. The determination of MIC and minimum bactericidal concentration (MBC) of the extract using microdilution method showed that such extract had MICs for lessThan i greaterThan B. cereus lessThan /i greaterThan , lessThan i greaterThan E. lessThan /i greaterThan lessThan i greaterThan coli lessThan /i greaterThan , and lessThan i greaterThan S. aureus lessThan /i greaterThan of 0.039, 0.312 and 0.156 mg/ml, respectively; and MBCs for lessThan i greaterThan B. cereus lessThan /i greaterThan , lessThan i greaterThan E. lessThan /i greaterThan lessThan i greaterThan coli lessThan /i greaterThan , and lessThan i greaterThan S. aureus lessThan /i greaterThan of 0.039, 0.625 and W. WUTITHAMAWECH , M. TANTIRUNGKIJ AND P. LIANGSAKUL Antibacterial potential, Thai medicinal plants, Clerodendrum inerme, Antipathogenic activity 412-421