Antibacterial and Larvicidal Activity of Ethyl Acetate Extract of Actinomycetes from Soil Samples

Abstract

This study aimed to explore the antibacterial and larvicidal potential of actinobacterial strains isolated from soil samples of Pakistan. Out of fourteen purified actinobacteria, antibiotic susceptibility profile confirmed five isolates showing resistance against tested antibiotics (ampicillin; lincomycin; rifampicin and erythromycin). Ribotyping confirmed that these isolates belong to Streptomyces species and were identified as S. monticola, S. septentrionalis, S. polaris, S. desertarenae and S. lutosisoli. Primary screening of the five isolates using cross streak method showed excellent zone of inhibition (ZI 10-27 mm) against tested pathogens (Escherichia coli, Klebsiella pneumoniae, Bacillus licheniformis, Pseudomonas aeruginosa and Bacillus subtilis). Secondary screening using ethyl acetate extracts also showed significant ZI in the range of 06 – 14.0 mm (P ≤ 0.05) against these pathogens thus confirming their bioactive potential. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of screened Actinomycetes was in the range of 1.3 - 3.5 mgmL-1 and 1.9 – 4.0 mgmL-1 of bacterial biomass, respectively. Three isolates, S. monticola, S. septentrionalis and S. polaris showed 100 % mortality at 1000 ppm against Anopheles 3rd instar larvae. These findings indicated that actinobacterial isolates possess antibacterial and larvicidal potential. Further extraction and purification of bioactive components from these bacterial may be a good source of novel antibiotics and natural-insecticides.