Potentially pathogenic and antibiotic resistant bacteria in the Danube Delta aquatic ecosystem

Abstract

Human and animal pathogenic and potentially pathogenic bacteria are constantly released into water waste system and from there to the environment. These microorganisms are able to mix acquiring new resistance by horizontal gene transfer (shuffling of genes and mobile genetic elements). At the same time, antibiotics are released into water and might exert selective activities as well as ecological damage in water communities, resulting antibiotic resistance. Water constitutes not only a way of dissemination of antibiotic resistant organisms among human and animal populations because drinking water is produced from surface water, but also a route by which resistance genes are introduced in natural bacterial ecosystem. Pollution of water resources is a major risk to human health and water quality throughout the world especially when the aquatic ecosystem is a part of a protected area. The main goal of the present paper was to monitor the occurrence of antibiotic resistant bacteria in the Danube Delta aquatic ecosystem. The experimental study was performed in 2014 on St. Gheorghe branch, the oldest branch of Danube Delta. The surface water samples were seasonally collected from eleven control sections with anthropogenic potential risk that could influence the water quality. The fecal indicators such as coliforms and enterococci were quantitatively assessed and antibiotic resistant bacteria were identified by disc diffusion method. Results indicated that the density of Gram-negative bacteria was higher than density of enterococci during the monitoring period. The isolated strains exhibited high rates of β-lactam-resistance especially to ampicillin and amoxicillin plus clavulanic acid and similar resistant phenotypes were consecutively identified from the same control section.