Screening of antibiotic sensitivity, antibacterial and enzymatic activities of microbes isolated from ex-tin mining lake

Abstract

Water sample from ex-tin mining lake was collected and cultured on nutrient agar (NA). Morphology characteristics revealed that isolates WL1 and WL4 were Gram-negative cocci and WL3 was Gram-positive cocci. Meanwhile, WL2 and WL5 were Gram-positive bacilli and spore formers. These isolates were screened for their antibiotic sensitivity against 17 types of antibiotics using Kirby-Bauer method. Antibacterial activity against 11 types of indicator bacteria were also tested using agar well diffusion method. The antibiotic susceptibility test demonstrated that all five isolates had high degree of inhibition to five types antibiotics namely amikacin, kanamicin, gentamicin, norfloxacin and tetracycline. Gram-negative cocci WL4 is a multiple resistant isolate that resistant to 10 types of antibiotics. The Gram-positive bacilli WL2 had antibacterial activity against Gram-negative Escherichia coli. Enzymatic assay showed that all isolates were proteolytic, lipolytic and phosphatase enzyme producers. Amylolytic activity was absent in all isolates. Protease, leucine arylamidase, alkaline and acid phosphatases, phospholipase esterase and esterase lipase were found in all isolates. The preliminary survey demonstrated that the water environment in the vicinity of Campus Lake is a reservoir of microbial populations. The present work concerns a screening of a few selected isolates with some significance importance in the application of medical and industry fields. In conclusion, the multi resistance isolates were not suitable for industry application due to some facts that it might produce toxic compounds and cause infection. The antimicrobial substance and enzymes produced by the potential isolates could be further screened for clinical application and mass production in industry. However, they must be evaluated for their safety and toxicity to human, animals and the environment. Key words: nutrient agar (NA), Kirby-Bauer, antibacterial assay, antibiotic susceptibility test, enzymatic assay.