Abstract
Antibiotic resistance of bacteria is an emerging problem in drinking water treatment. This paper presents the comparison of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) prevalence during the summer and winter season in a full-scale drinking water distribution system (DWDS) supplied by two water treatment plants (WTPs). The effect of distance from WTP and physical–chemical water parameters on its microbial properties was also tested. Bacterial consortia dwelling in bulk tap water were additionally compared by means of denaturating gradient gel electrophoresis (DGGE). The results showed that among ARB, bacteria resistant to ceftazidime (CAZ) were the most abundant, followed by bacteria resistant to amoxicillin (AML), ciprofloxacin (CIP), and tetracycline (TE). Numerous ARGs were detected in tested tap water samples. Only CAZ resistant bacteria were more prevalent in the season of increased antibiotic consumption, and only AML resistant bacteria relative abundances increase was statistically significant with the distance from a WTP. The investigated tap water meets all legal requirements. It is therefore safe to drink according to the law. Nevertheless, because antibiotic resistance could pose a threat to consumer health, it should be further monitored in DWDSs.
Highlights
Antibiotic resistance of bacteria has become a global problem, posing a serious threat to human health and life [3,4]
Escherichia coli, Clostridium perfringens were found in any sample, and the total number of bacteria was lower than established in the guidelines [68], suggesting sufficient water disinfection in water treatment plants (WTPs) and within the distribution system
Various genes were detected in finished water and recipients’ tap water samples, including antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) genes, suggesting potential for horizontal gene transfer (HGT) occurrence in the distribution system
Summary
Antibiotic resistance (in this paper, the term antibiotics refers to all substances with antibacterial properties, produced by microorganisms, synthetically or semi-synthetically [1,2]) of bacteria has become a global problem, posing a serious threat to human health and life [3,4]. Bacterial resistance can develop and disseminate via mutations and horizontal gene transfer (HGT) [2,7]. Developed or acquired resistance can be further disseminated between clinical and natural environments. -called ‘superbugs’, can be divided in two groups, namely well-known pathogens of clinical relevance, and opportunistic pathogens of environmental origin, frequently intrinsically resistant to multiple antibiotics, and posing a threat to immunocompromised patients [10]. Soil and water, have become recognized as recipients, reservoirs, and sources of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) of clinical concern [2,11,12].
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