Susceptibility of Some Pathogenic Microbes to Soft Tissue Extract of the Mud Clam, Polymesoda Expansa (Bivalvia: Corbiculidae)

Antibiotic resistance of microbes has led to the search for potential sources of bioactive compounds with antimicrobial properties. The innate defense mechanisms of aquatic invertebrates against pathogenic organisms have made them prime candidates for extraction of microbicidal compounds. The mud clam (Polymesoda expansa) successfully thrives in an environment full of pathogenic microorganisms. An experiment on the antimicrobial activity of the clam was conducted to determine its potential as a source of antimicrobial compounds. Antimicrobial activity of various concentrations of the ethanolic crude extract (ECE) of P. expansa was tested against the bacteria Escherichia coli (gram-negative), Staphylococcus aureus (gram-positive), and the fungus Candida albicans using standard discs diffusion technique. The ECE showed 24-h activity on E. coli with inhibition zone (IZ) range of 27.65 to 32.57 mm. Similar IZ range (28.73–32.08 mm) was observed in S. aureus test cultures, however the efficacy time of the ECE was only 7 h. C. albicans test cultures showed low activity of ECE with IZ range of 0.00 to 12.75 mm and efficacy time of 8 h. The study showed that P. expansa is a potential source of antimicrobial compounds.