Assessment of the Prevalence of Antibiotic-Resistant Bacteria and the Concentration of Antibiotics in EU Bathing Waters in Western Germany

Recreational use of bathing waters is very popular in Germany and the European Union (EU). Therefore, the spread of antibiotic-resistant facultative-pathogenic bacteria (ARB) presents a possible public health issue. During the 2018 summer bathing season, a prevalence study involving 16 selected EU bathing waters in North Rhine-Westphalia was conducted. The aim was to identify the presence of ARB, antibiotic residues or resistance genes, and to develop a tool that assists advisers on prevention measures for individuals and the health authorities. The study included (i) hygienic-microbiological analyses according to the EU Bathing Water Directive, (ii) antibiotic residue measurements, (iii) cultural and molecular analyses to identify ARB and resistance genes and (iv) development of a risk assessment tool based on the burden of the bathing water and the vulnerability of bathing persons. All bathing waters were complied with the EU Bathing Water Directive. Three samples were found to contain very small amounts of ARB. Small quantities of antibiotic residues were detected in three bathing waters. Only one sample contained a resistance gene. In total, only 2 bathing waters were assumed to be systemically burdened with ARB and antibiotic residues or resistance genes. 4 bathing waters indicated single contamination events, 10 bathing waters were unburdened. In conclusion, bathing waters fulfilling criteria of the EU bathing water directive did not show high contaminations with ARB, antibiotic residues or resistance genes. However, we propose that people with risk factors should avoid swimming in burdened waters; people with immune deficiency should avoid swimming at all.