Antibiotic resistance of coliform bacteria in marine water and bivalve from Zanzibar Island

Antibiotic resistance is a critical global health issue, especially in resource-limited countries like Tanzania. This study assessed coliform prevalence and antibiotic resistance in marine water and bivalves from Zanzibar Island. A total of 60 samples were collected on March 2024 for the period of one week at six different sites. The enumeration of coliform bacteria was done on M-Endo agar. Antimicrobial testing was conducted on eight antibiotic types, with resistance genes identified through polymerase chain reaction (PCR) using specific primers. In marine water samples, coliform loads varied from 4.67 × 102 CFU/mL to 1.00 × 104 CFU/mL, while for bivalves, it was between 7.30 × 103 CFU/g and 1.28 × 105 CFU/g. Coliform load differences presented significant difference among water samples with F = 6.866, p = 0.00304 and insignificantly in the bivalve samples, F = 2.048, p = 0.143. Bivalve samples depicted significantly higher levels of contamination, t = 2.6025, p = 0.01858. High resistance was recorded against methicillin 91.67% and ampicillin 75.00%. Mostly detected resistance genes were; tet_A 36.17%, bla_EBC 31.91%, gyr_A 29.79%, and mphA 14.89%. Findings from this study showed alarming levels of environmental contamination with a high level of antibiotic resistance in the marine ecosystems of Zanzibar.