Exploring Marine Microorganisms for Antibacterial Activity against Pathogenic Bacteria: A Susceptibility-Based Approach

Abstract

Aim: To isolate and identify marine microorganisms, assess their antibiotic sensitivity patterns against commonly used antibiotics, and evaluate their potential antibacterial activity against pathogenic Staphylococcus aureus and Escherichia coli. Study Design: This study investigated the diversity, antimicrobial resistance (AMR), and antibacterial potential of marine microorganisms isolated from Coco Beach, Dar es Salaam, Tanzania. Water samples were randomly collected from three different sites along the beach at depths of 0.5–1.0 meters using pre-sterilized bottles. Samples were transported in a cool box to the Pharmaceutical Microbiology Laboratory at Muhimbili University of Health and Allied Sciences for analysis. Duration of Study: The study was conducted between February 2025 and June 2025. Methodology: Conventional microbiological methods were used for the isolation and identification of microorganisms. Antibiotic sensitivity testing was performed using the Kirby–Bauer disc diffusion method on the Mueller Hinton agar. Discrete marine microbial colonies were sonicated, and the resulting suspensions were screened for antibacterial activity against pathogenic S. aureus and E. coli. Results: A total of 63 water samples yielded 73 marine microorganisms, categorized into Vibrio cholerae, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Aspergillus flavus, and Rhizopus species. V. cholerae was the predominant organism, accounting for 56 of the 73 isolates. Antibiotic resistance levels ranged from 30% to 100%. All fungal isolates were resistant to fluconazole, while Rhizopus species also showed resistance to amphotericin B. Notably, seven microbial suspensions (9.6%) demonstrated antibacterial activity against pathogenic S. aureus and E. coli, with most activity observed among V. cholerae isolates. Conclusion: The marine microorganisms from Coco Beach exhibit high levels of antibiotic resistance but also possess notable antibacterial potential. Further research is recommended to identify bioactive compounds and improve waste and pharmaceutical disposal practices to curb AMR spread and protect marine ecosystems.