Coastal sewage discharge and its impact on fish with reference to antibiotic resistant enteric bacteria and enteric pathogens as bio-indicators of pollution.

Presence of antibiotic resistant bacteria as bio-indicators of pollution was monitored in fish (colons and gills) and in sewage treated effluent (STE) in two marine sites in the Gulf of Oman, Muscat. One site was polluted as the sewage effluent STE was directly discharged into the sea while the unpolluted site was 10 km away. A total of 42 water samples (250 mL each) were collected from both sites. In the polluted site, 14 samples were taken directly from the STE discharge point and 14 from the surrounding area near the STE discharging point (7-10 m). Water and fish samples were collected from polluted and unpolluted sites. Chlorine and nitrate levels were significantly higher in STE samples. A significant difference (P<0.005) was found in total bacterial count of fish colon and gills in the two sites. Most probable number (MPN) was significantly higher in STE and polluted seawater over unpolluted. Coliforms were detected in the polluted site only. A total of 320 target enteric normal flora of animals and pathogenic species were isolated from 10 genera taken from water and fish samples. The isolates were exposed to 14 antibiotics. Most of the isolates were resistant to at least one antibiotic with ampicillin was the dominant antibiotic. This is a clear indication that sewage effluent causes contamination of marine wildlife along coastal lines.