Determination of Invitro Antimicrobial Activity of selected Marine Sponges found in Sri Lanka

Abstract

Indiscriminate use of antibiotics leads to drug resistance in microorganisms. Therefore, discovery of new molecules to challenge the drug resistance is critically important. Sponges have developed efficient defense mechanisms which largely depend on the production of chemical compounds against foreign attackers. The aim of this work is to study the antimicrobial activities of Clathria rugosa, Clathria foliacea, Acanthella acuta and Antho dichotoma, collected from Dehiwala, Sri Lanka, against ten human pathogens and to separate and study the active ingredients using Bioautographic TLC assay. Mixture of methanolic and dichloromethane extracts of all four sponges were prepared using cold maceration technique. Using the standard disc diffusion method, extracts were tested against five Gram negative bacteria which includes Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus mirabilis, Salmonella sp. and Escherichia coli, three Gram positive bacteria which includes Staphylococcus aureus, Methicillin Resistant Staphylococcus aureus (MRSA) and Staphylococcus saprophyticus and two fungal species namely Candida albicans and Aspergillus niger. Out of the sponges tested, only C. foliacea was active against S. aureus (Inhibition Zone Diameter = 11.7 mm) and MRSA (IZD= 9.0 mm). A. dichotoma was active against S. aureus (IZD = 9.0 mm), MRSA (IZD = 10.0 mm) and C. albicans (IZD = 13.0 mm). All Gram-negative bacteria, S. saprophyticus and A. nigerhave shown resistance to extracts of all four sponges. The best separation in TLC was observed with a mixture of Hexane, Toluene, Dichloromethane, Diethyl Ether, Methanol and Water mixed in a ratio of 2: 0.05: 0.6: 0.3: 0.1: 0.002. Among the 12 spots of A. dichotoma, visualized under UV light, six spots inhibited the growth of MRSA and all the spotshave shown the antimicrobial activity against C. albicans in TLC bioautography.Three out of seven visualized spots of C. foliacea were active against MRSA. Among the four sponges studied, A. dichotoma showed higher antimicrobial activity in terms of inhibition of bacterial growth, then number of microbial species inhibited as well as higher number of antimicrobial compounds. None of sponges tested were active against Gram negative bacteria in the microbial panel used. S. aureus was the most susceptible pathogen among the tested microorganisms. Even though, S. aureus and MRSA were susceptible for two sponge extracts, S. saprophyticus has shown resistance for all the sponge extracts tested.