The research was performed to investigate the in vitro antibacterial effect of Clerodendrum fragrans vent. (roots, branches and leaves) extract on 2 pathogenic bacteria (E. coli and Salmonella spp.) isolated from feces of diarrheainfected piglets. The experimental clinical treatment of the extracts was also performed on diarrhea piglets. The results showed that ethanol 70 percent branch extract possessed the best in vitro antibacterial effect on both of tested bacteria with the largest diameter of inhibitory zone (E. coli - 23 mm and Salmonella spp. - 25 mm), while the root extract had only small inhibition zone and leaf extract had no inhibition zone. the authors compared the efficacy of Clerodendrum fragrans vent. branch by different extract solvents, including ethanol 35 percent, ethanol 70 percent, axit acetic 5 percent and aceton 70 percent. All of these branch extracts showed in vitro inhibition effect with E. coli and Salmonella spp., in which ethanol 35 percent extract possessed the best effect, shown by the largest diameter of inhibitory zone (E. coli -30,67 mm
Salmonella spp. - 32,33 mm). Ethanol 35 percent extract also had good in vitro antibacterial effect with large inhibitory zone (20mm) on E. coli with antibacterial resistant palsmid (kanamycin resistant E. coli Top 10 pPS1
ampicillin resistant E. coli Top 10 pJET 1.2/blunt). The experimantal clinical treatment of ethanol 35 percent Clerodendrum fragrans vent. branch extract on diarrhea piglets also showed good results.