Isolation, characterisation and antimicrobial screening of compost Actinomycetes using a modified resazurin based assay
2011
Low, Anis Low Muhammad | Sharifah Aminah Syed Mohamad | Mohd Faiz Foong Abdullah
This study aims to isolate, characterise the biodiversity of compost actinomycetes and to investigate antimicrobial activity of the isolates. A total of 118 putative actinomycete isolates were recovered from 2 types of compost sample collected from various animal farms in Selangor, Malaysia. All isolates were subjected to preliminary screening of direct broth by disc diffusion method against Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), Bacillus subtilis (ATCC 6633), Staphylococcus aureus (ATCC 29213), Candida albicans and Saccharomyces cereviseae. 31 (26.3%) of the isolates exhibited antimicrobial activity against at least one of the test microorganisms. The results indicated that almost all of the active isolates (71.0%) inhibited the growth of B. subtilis. Isolate G1A6 displayed highest zone of inhibition on both C. albicans (17.0 mm) and S. cerevisiae (15.5 mm) whereas isolate G2A2 inhibits all test pathogens except for P. aeruginosa. A modified microtiter plate based assay incorporating resazurin as cell growth indicator was then developed and used to screen the ethyl acetate extract of 41 isolates against B. subtilis, S.aureus, E. co/i and C. albicans. 31 extracts (75.6%) were found to be effective in inhibiting at least one of the strains tested with the highest inhibitory against B. subtilis (63.4%). Moreover, extract of G1A30 exhibited inhibitory against all strain tested. Generally, most isolates that showed antimicrobial and antifungal properties in direct broth screening also displayed active extracts. The results demonstrated that the resazurin microtiter plate assay is a simple, fast and reliable method that could be used to conduct antimicrobial screening of microbial extracts.
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