Antimicrobial Activity of Ficus vogelii Miq and Boerhaavia diffusa Linn against Multidrug-Resistant Respiratory Pathogens with Bactericidal Kinetics and Cytotoxicity

Abstract

Introduction: Respiratory tract infections (RTIs) are some of the most common and significant health-related issues seen in clinical medicine. Many studies have shown that comorbid illnesses are associated with acute respiratory tract infections. The effectiveness of available antimicrobial drugs has decreased as a result of the resistance of microrganisms to synthetic drugs. The therapeutic potential of medicinal plants as an alternative to synthetic antibiotics is currently being investigated. Ficus vogelii Miq and Boerhaavia diffusa Linn have been used in ethnomedicine for the treatment of diseases of microbial origin. Methodology: The pulverized leaves of F. vogelii and Boerhaavia diffusa were extracted by cold maceration with methanol and partitioned into hexane, ethyl acetate and methanol.  Antibiogram profile of clinical isolates from RTIs was determined by disc diffusion method. Antimicrobial activity of the extracts and fractions of the plants was determined by agar well diffusion. Bioassay-guided fractionation of the most active fractions was carried out using vacuum liquid chromatography (VLC). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by microbroth dilution. Bactericidal kinetics was done using the viable count technique. Cytotoxicity of the plant extracts was determined using the brine shrimp assay. Results: The antibiogram profile of the microbial isolates showed that 85% of the isolates were multidrug-resistant. MIC values for both plants ranged between 1.5625 mg/mL to 25 mg/mL. Bactericidal kinetics showed a complete kill of S. aureus by the ethyl acetate fraction of F. vogelii Miq at concentrations of 12.5mg/ml and 25mg/ml in 2 hrs while a total kill of E. coli was achieved in 3 hrs by the hexane fraction of B. diffusa the brine shrimp lethality assay revealed that the fractions of both plants were non-toxic. Conclusion: F. vogelii and B. diffusa possess antimicrobial activities and the non-toxicity of the active fractions implies the safety of the plants as alternative drug agents to synthetic antibiotics.