Antimicrobial activity of marigold (Tagetes erecta), mulberry (Morus indica), and red shallot (Allium ascalonicum) extracts against Streptococcus agalactiae

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 antibiotics. Nowadays, there are many efforts to minimize the misuse of antibiotics. This study evaluated the antimicrobial activity of the 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 the crude extracts using absolute ethanol from three Thai herbs was tested against standard strains of S. 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 that all four groups of Thai herbal extract had inhibitory activity against standard strains of S. agalactiae. The inhibitory concentration test values were obtained using the dilution test at 25, 50, and 75  mg/ml. The maximum antimicrobial activity against S. agalactiae was observed in the 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 of S. agalactiae and suggesting that they may be useful in the treatment of S. agalactiae infections in humans and animals.