SCREENING OF ANTIBIOTIC PRODUCING ACTINOMYCETES FROM THE SOIL SAMPLES AND ANTIBACTERIAL ACTIVITY IN VARYING SODIUM NITRATE CONCENTRATION

Abstract

Actinomycetes are gram positive filamentous, slow growing bacteria, best known to produce antibiotic. The aim of this study was to screen antibiotic producing actinomycetes and determine its antibiotic activity against ATCC cultures at different gradient of NaNO3. This study was carried out from March 29 to April 28, 2022. Thirty collected samples were collected and transported and processed in Amrit campus. Primary and secondary screening were performed by perpendicular streaking and agar well diffusion method respectively. Characterization and identification of the isolated actinomycetes were performed. From thirty collected samples, twenty-eight samples were actinomycetes. Only two samples were antibiotic producing actinomycetes MI410 -3 and NP110 -2 showed antibacterial activity against ATCC cultures viz: S. aureus 43300, E. coli 35218, E. coli 25922 and Klebsiella 700603 in primary screening. Antibiotic was produced by sub-merged state fermentation with varying concentration of NaNO3 and secondary screening was done by agar well diffusion against ATCC cultures in comparison to standard streptomycin (100 µg/mL). In comparison to standard streptomycin (100 µg/mL) extract MI410-3 with 1% NaNO3 was effective only against E. coli 25922 while NP110-2 with 0.5% NaNO3 against E.coli 35218 (14.67mm), E.coli 25922 (19.67mm) and S. aureus 43300 (17mm) whereas NP110-2 has also shown antibacterial effect with 1.5% NaNO3 against E. coli 35218 (13mm), Klebsiella spp. ATCC 700603 (11.5mm) and S. aureus 43300 (12.5mm). Statistically, there is significant difference at 5% level of significance between the sample concentration at 0.5% of NaNO3 (.001, P<0.05) and 1.5% of NaNO3 (0.024, P<0.05) in antimicrobial activity. However, there is no significant difference at 5% level of significance between the sample concentration at 1% (0.356, P>0.05). The isolated actinomycetes was presumed as Streptomyces spp. Both MI410-3 and NP110-2 (7.14%) showed antibacterial activity against cultures in primary screening. The indigenous species of actinomycetes, isolated from various places of Kathmandu valley can be used in industrial production of antibiotics which can help in economic growth of Nepal.