Identification and Antimicrobial Potential of Marine Sponges ( <i>Carteriospongia foliascens</i> , <i>Callyspongia fallax</i> , and <i>Paratetilla arcifera</i> ) from Kenyan Marine Waters

Emerging and re-emerging infectious diseases and pathogens present a significant global public health threat that has led researchers to focus on discovering new antimicrobial agents in order to address the challenge. Sponges are a promising source of marine natural products, which can be used as lead molecules for drug discovery. This study was aimed at identifying marine sponges through morphological and molecular techniques and evaluate the bioactivity potential of their organic crude extracts against <i>Escherichia coli</i>, <i>Staphylococcus aureus</i>, <i>Pseudomonas aeruginosa</i>, and <i>Candida albicans.</i> Deoxyribonucleic acid (DNA) barcoding of the cytochrome c oxidase subunit I (COI) gene identified three genera of sponges (<i>Carteriospongia</i>, <i>Callyspongia</i>, and <i>Paratetilla</i>). Disk diffusion assay was used to determine the inhibition zone diameter (IZD) of the sponges' extracts. Minimum inhibitory concentrations (MICs) and the minimum bactericidal/fungicidal concentrations (MBCs/MFCs) of the most active sponge extracts were determined. The bioactive compounds were analyzed using gas chromatography-mass spectrometry (GC-MS). The dichloromethane extracts of <i>Carteriospongia foliascens</i> demonstrated the highest antifungal activity against <i>C. albicans</i> (31.33 ± 1.2 mg mL^-1), surpassing the standard drug fluconazole (29.33 ± 1.5 mg mL^-1). The MIC values for the sponge extracts ranged from 3.86 to 5.89 mg mL^-1, and the ethyl acetate extract of <i>Callyspongia fallax</i> had an MBC of 4.03 mg mL^-1 against <i>S. aureus</i>. GC-MS chromatogram identified 98 compounds across 41 classes in three sponge extracts. Notably, 9.2% of these compounds have been reported to exhibit antimicrobial activity against human pathogens. This study confirms that sponges are a source of useful biochemicals, which have potential for drug discovery. To the best of our knowledge, this is the first comprehensive study to report on the characterization of marine sponges from the Kenyan waters. Further research work to structurally elucidate and identify the most active bioactive compounds from the extracts of <i>C. foliascens</i> and <i>C. fallax</i> is recommended.