Antibacterial Activity of Actinomycetes Isolated from Waste Dump Soil from Western Uganda

Abstract

Aims: To determine the antibacterial activity of actinomycetes isolated from waste dump soil in Western Uganda. Study Design:  The study was an experimental laboratory design. Place and Duration of Study: Waste dump soil samples were collected from Bushenyi, Kabale, Kasese, and Mbarara districts  in Western Uganda, from May, 2016 to February, 2017. Methodology: Actinomycetes were isolated from 22 waste dump soil samples collected using standard spread plate technique, all isolates were screened primarily using cross streak method against Escherichia coli ATCC25922, Pseudomonas aeruginosa ATCC27853, and Staphylococcus aureus ATCC25923, resistant clinical bacteria: Escherichia coli 2966, Pseudomonas aeruginosa 2929, and Staphylococcus aureus 2876 (MRSA). Secondary screening was carried out by first growing all fifty six isolates (56) in broth media and their supernatants were tested for activity using agar well diffusion method. The remaining broths were extracted using ethanol. The ethanol extract was also tested for antibacterial activity using agar well diffusion method. The MIC was determined using tubes dilution technique and MBC was determined by culture method. Results: Fifty six (56) actinomycetes isolates were isolated from 22 waste dump soil samples. Four (7.14%) isolates showed activity to at least one test bacteria during primary screening.  Eight (14.29%) actinomycetes isolates fermented broth showed activity to at least one test bacteria during secondary screening, with mean zone of inhibition of 7.67±1.45 to 33.67±2.03 mm. Isolate KBMWDSb6 showed activity to all test bacteria with exception of resistant Staphylococcus aureus 2876 (MRSA) while isolates BRWDSc (SP) and KBRWDSa3 (RF) showed activity to all sensitive standard isolates and resistant Staphylococcus aureus 2876 (MRSA). Eleven (19.64%) actinomycets isolates ethanol extracts showed activity to at least one test bacteria with mean zone of inhibition 7.33±1.20 to 31.67±1.45 mm. The MIC and MBC of the extracts were found to be 0.07 to 0.62mg/mL and 0.15 to 1.25mg/mL respectively. Conclusion: The findings of this study indicated that actinomycetes spp isolated from waste dump soil collected from Western Uganda have ability to produce bioactive compounds with activity against bacteria including clinically drugs resistant bacterial isolates. This could be a good source of novel antibiotics.