Identification and validation of anti-microbial properties of some tropical folklore medicinal plant species against some multi-resistant bacterial pathogens

Bacterial resistance is rapidly emerging worldwide and endangering the efficacy of commercial antibiotics. Scientific interventions are greatly needed to find out natural sources which can be used to manage antibiotic resistance crisis. Traditional healers from the Borneo were directly interviewed for selecting ethnomedicinal flora and antibacterial action of identified plant species were explored. Plant extracts were obtained by four different extraction techniques viz. grinding with 95% ethanol, decoction (boiling), cold infusion and blending, and were tested against multi-resistant bacterial species (Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli) through two bioassays viz. agar well diffusion and disc diffusion methods. The results revealed that 19 plant species out of 35 exhibited antimicrobial activity against B. cereus and S. aureus while 15 showed activities against P. aeruginosa and E. coli. Among all plants, Anacardium occidentale extract made by decoction method depicted a maximum zone of inhibition (2.0 cm) against P. aeruginosa in both disc diffusion and well diffusion techniques. However, the zone of inhibition against P. aeruginosa recorded with five commercial antibiotics i.e., Erythromycin, Ceftriaxone, Streptomycin, Amoxicillin and Penicillin was 0, 1.6, 0.4, 0 and 0.2 cm, respectively. Thus, Anacardium occidentale can represent a natural alternative against this multi-resistant bacterial strain. Our study also verified that some tropical plant extracts have the potential to cure important bacterial infections and need further investigation for proper drug development, medication, and administration from the perspectives of safety, efficacy and pharmacoeconomics.