Determination of heavy metal resistance levels in Escherichia coli isolated from mediterranean mussel and sea snail in Eastern Black Sea

Marine environment is exposed to various pollutants such as heavy metals, pesticides and antibiotics. Bacterial resistance to these pollutants is a global problem all over the world. In this study, Mediterranean mussel (Mytilus galloprovincialis) and sea snail (Rapana venosa) were seasonally collected from 12 sampling points from Artvin, Rize, Trabzon and Giresun Coasts of Black Sea, Turkey. A total of 54 Escherichia coli isolates (35 from mediterranean mussel and 19 from sea snail) were isolated from Mytilus galloprovincialis and Rapana venosa. The bacteria were tested for their ability to tolerate Cu (Copper), Cd (Cadmium), As (Arsenic) and Hg (Mercury). For this purpose, minimum inhibitory concentration (MIC) tests for all isolates to the Cu, Cd, As and Hg were done to determine heavy metal tolerance or resistance using broth dilution technique. MIC concentration for Cu, Cd, As and Hg ranged between 100-400 mg/l, 100-200 mg/l, 25-400 mg/l and 3.125-25 mg/l, respectively. All of the strains were resistant to Cu, but sensitive to As. Resistance to Hg was determined as 7.4 %. The most common heavy metal resistance gene in the bacteria was nccA and followed by chrB and merA. Tolerance or resistance of the bacteria to toxic pollutants including heavy metals is of significant ecological importance. These bacteria could be used as an indicator for controlling environmental heavy metal pollution.