Antibiotic resistance markers among Gram-negative isolates from wastewater and receiving rivers in South Romania

Abstract

This study investigated the resistance profiles of Gram-negative strains isolated from different types of wastewater and the receiving river. Significantly higher resistance rates were observed in strains from river receiving wastewater treatment plant (WWTP) effluent as compared with strains from upstream river. High multidrug resistance rates were registered in E. coli (60.34%), Enterobacter (34.38%) and Klebsiella (32.76%) strains. Strains isolated from river receiving WWTP effluent harboured blaCMY, blaNDM, tetD, sulI and qnrB genes. The blaTEM, blaSHV and blaCMY genes were detected in 10% to 40% of wastewater strains. The tetB was the most frequent in WWTP effluent (75%), WWTP influent (42.85%) and hospital effluent (33.33%). The sulI gene was the most common (2056.25%) in all wastewater types, followed by sulII (9.09-16.66%). The qnrB (60%) and qnrS (33.33%) genes were detected in strains isolated from hospital effluent. The results of this study showed that wastewater treatment process might increase the antibiotic resistance of WWTP bacteria. The bacterial strains isolated from the WWTP effluent exhibited about 50% of the 18 investigated resistance genes, which could be further disseminated among environmental bacteria.