Antimicrobial Activity Screening of Bacteria Isolated from Tasik Cermin

Abstract

Introduction: With the emergence of the multi-drug resistant bacteria that threaten the human health, novel antimicrobial compounds from natural environment have been increasingly explored. Tasik Cermin is a lake completely covered by karst towers and hills and lacks any inflow or outflow of water making it an oligotrophic environment with limited nutrient availability. Increased competition among microorganisms leads to production of antimicrobial compounds that can inhibit the growth of its competitor. Thus, the aim of this study is to assess antimicrobial activity of bacterial isolates from Tasik Cermin and identify the most resistant isolate. Methods: The isolates were tested against five test bacteria: Staphylococcus aureus, Bacillus subtilis, Streptococcus pneumoniae, Escherichia coli, and Proteus vulgaris by primary screening through perpendicular streak method, secondary screening followed by MIC and MBC and the most resistant bacteria was identified by molecular identification. Results: The result indicates that only one isolate (Isolate TC1A) was able to show potential antimicrobial activity against P. vulgaris and S. pneumoniae. This isolate was further tested by secondary screening through agar well diffusion method and inhibition zone were observed on P. vulgaris (14.97 ± 0.05), E. coli (9.23 ± 0.25) and S. pneumoniae (14.93 ± 0.12). Statistical analysis by One-Way ANOVA and Tukey test method indicates that inhibition zone of E. coli is significantly different as compared to S. pneumoniae and P. vulgaris. Molecular identification revealed that the isolate TC1A was identified as Achromobacter sp. with 97.68% similarity percentage. Conclusion: This finding shows that bacterial isolates from under-explored areas have the potential of producing novel antimicrobial compounds.