Abstract

Abstract
Background and Aim: The increasing antimicrobial resistance with reduced susceptibility to antimicrobial drugs is becoming a major concern for both human and animal which raises health morbidity and mortality rate of cases that cannot be treated by antimicrobial drugs. Nowadays, there are many efforts to minimize the use of antimicrobial drugs. This study evaluated the antimicrobial activity of crude ethanolic extracts of three Thai herbs divided in four groups; petals of marigold (Tagetes erecta), mulberry leaves and root barks (Morus indica) and whole onions of red shallot (Allium ascalonicum) against Streptococcus agalactiae.
Materials and Methods: The antimicrobial activity of four groups of crude extracts using absolute ethanol from three Thai herbs were tested against standard strains of Streptococcus agalactiae using the Agar well diffusion method. The commercial antibiotics ceftriaxone and erythromycin were used as positive control standards to determine the sensitivity of S. agalactiae.
Results: The result showed all four groups of Thai herbal extract had inhibitory activity against standard strains of Streptococcus agalactiae. The MIC values were obtained using the dilution test at 25, 50 and 75 mg/ml. Maximum antimicrobial activity against S. agalactiae was observed in ethanolic extracts from red shallot extract followed by leaves of mulberry, petals of marigold and root barks of mulberry, respectively.
Conclusion: The results demonstrated that the crude extract of three Thai herbs had antimicrobial activity inhibiting the growth S. agalactiae and suggesting that they may be useful in the treatment of S. agalactiae infections in humans and animals.

Key words: antimicrobial activity, ethanol extract, Thai herbal extracts, Streptococcus agalactiae