In vitro interaction of antimicrobial agents in combination with plant extract against multidrug-resistant bacterial strains

ABSTRACT

Aims: To evaluate the possible in vitro interaction between methanolic extract of root of Adiantumcapillus-veneris and certain known antimicrobial drugs i.e. Oxacillin, Ceftazimide, Cefriaxone, Ofloxacin, Meropenem, Erythromycin, Cefuroxime, Cefoxitin, Cefotaxime and Ampicillin. Methodology and results: The study was carried out against ten bacterial strains (Staphylococcus aureus, S. epidermidis, Salmonella typhi, Klebsiella pneumoniea, Shigella dysentriea, Proteus vulgaris, Pseudomonas aeruginosa, Providencia species, Citrobacter freundii and Escherichia coli isolated from urine, pus and blood samples. Both disc diffusion and well diffusion methods were used to determine antimicrobial activity of plant extract in combination with antibiotics. Antimicrobial sensitivity showed that Meropenem was the most effective antibiotic with zone of inhibition (ZI) of 25-33 mm among all tested antibiotics followed by Ofloxacin (10-26.5 mm), Ceftriaxone (8-20 mm), while Oxacillin showed no activity against almost all bacterial strains. The study showed that most bacterial strains were resistant to most of the antibiotics used, ranging from 20-60%. The methanolic extract (mEXT) of A. capillus-veneris used alone was active against most of the bacterial isolates with maximum activity against E. coli with 16 mm ZI. The study also indicated that there was an increased activity in case of combination of mEXT with antibiotics. The combined effects of plant extract with antibiotics were synergistic against most of the bacterial strains. The mEXT showed maximum synergistic effect with Ceftazimide with ZI of 42 mm followed by Meropenem (40 mm) and Ceftriaxone (28 mm) against multidrug-resistant (MDR) bacterial strains. Conclusion, significance and impact of study The data suggests that plant extract could be used as alternative to antibiotics. These results give scientific backing that combination between plant extract and antibiotics would be useful in fighting the emerging drug-resistant bacterial pathogens.