Inhibitory Effects of Plant Extracts and Putative Endophytic Actinomycetes from the Selected Members of Meliaceae Family against MDR Pseudomonas aeruginosa

Abstract

Aims: To isolate and screen endophytic actinomycetes and plant extracts from Azadirachta indica and Melia azedarach for antibacterial effects against MDR Pseudomonas aeruginosa. Study Design: Isolation and identification of the endophytic actinomycetes from plant tissues, cultivation of the selected strains, solvent extraction, screening of methanolic extracts for antibacterial activity against MDR Pseudomonas aeruginosa, chemical profiling of the extracts. Place and Duration: Department of Microbiology and Molecular Genetics, University of the Punjab, Lahore, Pakistan, during July 2014 to June 2015. Methodology: The endophytic actinomycetes were isolated by surface sterilization of the plant tissues. The methanolic crude extracts of the endophytic actinomycetes and extracts of plant tissues were prepared. Antibiotyping of the Pseudomonas aeruginosa was done using a panel of 13 antibiotics by disc diffusion assay. The antimicrobial activity of the methanolic extracts was determined by well diffusion assay, while the cytotoxicity of the extracts was determined by brine shrimp microwell cytotoxicity assay. The chemical profiling of the extracts was performed by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC/UV) analysis. Results: 20 endophytic actinomycetes strains were isolated and screened from the selected plants, among them 17 strains were found to be active against MDR Pseudomonas aeruginosa, with low cytotoxicity against Artemia salina. Antibiotics resistance profiling of the selected 21 Pseudomonas aeruginosa strains confirmed them as multidrug resistant (MDR) strains based on their multiple antibiotics resistance (MAR) values. Metabolic profiling of the extracts through, thin layer chromatography (TLC) and HPLC exhibited an impressive chemical diversity of the active constituents in the endophytic actinomycetes and plant extracts. Conclusion: The antibacterial activity of methanolic crude extracts of endophytic actinomycetes and plant tissues against MDR Pseudomonas aeruginosa depicted the selected plants (Azadirachta indica and Melia azedarach) as a promising source of commercially useful compounds to treat infections caused by MDR Pseudomonas aeruginosa.