Frequency of Antibiotic-Resistant Bacteria isolated from the Kınalıada Coastal Areas of the Sea of Marmara, Türkiye

In the process of global climate change, the negative effects of anthropogenic activities on microbial interactions have become more visible in coastal areas. Because island coastal ecosystems are fragile ecosystems that are open to dynamic environmental variables, it is important to determine bacteriological signals in these regions. The frequency of bacterial antibiotic resistance in aquatic ecosystems is a micro-marker of human activity. The frequency of antibiotic-resistant bacteria was investigated in surface water samples collected from the coastal areas of Kınalıada Island in the Sea of Marmara between 2018 and 2019. The bacteria isolated from the sea water were screened against: spectinomycin (SC300), nitrofurantoin (F50), Rifampicin (Rd2), tetracycline (TE30), ampicillin (AMP10), and oxytetracycline (OT30) using the disk diffusion technique. The frequencies of antibiotic-resistant faecal coliform, total coliform, intestinal enterococcus, and heterotrophic aerobic bacteria were evaluated according to the Clinical Laboratory Standard Institute (CLSI). The antibiotics to which all bacterial isolates showed the highest resistance were tetracycline and oxytetracycline (98.7% The frequency of resistant heterotrophic aerobic bacteria was recorded at 100% against all tested antibiotics. All bacterial isolates showed resistance to more than three antibiotic derivatives, and the Multiple Antibiotic Resistance (MAR) index was determined to be in the range of 0.67–1. The findings of this study provide regional evidence of the influence of anthropogenic pollution on the spread of antibiotic resistance. The detection of high levels of antibiotic-resistant bacteria indicated that the coastal areas of Kınalıada are at potential risk for the global spread of resistant bacteria, human health, and ecosystem function.