Antimicrobial Resistance of Heterotrophic Bacteria and Enterobacteriaceae Inhabiting an Anthropogenic-Affected River Stretch in Bulgaria

Abstract

The increasing antimicrobial resistance (AMR) of pathogens is a significant threat to human and animal health, but it is also an environmental challenge for water resources. The present study aimed to quantify heterotrophic bacteria resistant to five groups of antibiotics (ABs) in a selected Yantra River stretch (including its tributary, the Belitsa River); to assess AMR prevalence among Enterobacteriaceae; and to assess the impact of urban effluents or rural runoff on AMR prevalence along the river course at eight sampling points. Culture-dependent methods were used in a population-based study of total AMR and for AB susceptibility testing of Enterobacteriaceae isolates. The data reveal significant differences in AMR dissemination and a lower (up to 10%) proportion of different types of antibiotic-resistant bacteria (ARB) in the Yantra River water compared to the Belitsa River (up to 20%). The incidence of resistant Enterobacteriaceae isolates was in the range of 1% to gentamicin to 36% to ampicillin, including multidrug resistance of 19%, and different AMR patterns of isolates from each river. The prevalence of AMR among aquatic bacteria highlights the need for adequate waste water treatment and for management, monitoring and control of treatment processes to limit anthropogenic pressure through discharge of untreated or incompletely treated waste water and to ensure the ecological well-being of receiving waters.

Metagenomic Investigation of the Short-Term Temporal and Spatial Dynamics of the Bacterial Microbiome and the Resistome Downstream of a Wastewater Treatment Plant in the Iskar River in Bulgaria

“…At the time of writing, in Bulgaria there was only one published study from 2017 on 16S rRNA metagenomic profiling of the bacterial freshwater communities in two Bulgarian reservoirs [ 46 ], showing the vastly unexplored area. In regard to AMR, a few attempts to detect AMR in water bodies could be listed; however, all of them were culture-based studies [ 47 , 48 , 49 , 50 ], therefore with limited potential for a more detailed description of both the microbial communities and their ARGs. Lastly, one molecular-based targeted detection study was published on the freshwater Iskar Dam that is located downstream of our sampling locations; however, the study focus was water-borne pathogens with emphasis on nontuberculose mycobacteria [ 51 ].…”