The Prevalence of Antibiotic-Resistant Fecal Bacteria in Recreational Aquatic Environments: Phenotypic and Molecular Approach

The rising incidence of antibiotic resistance poses a significant threat to public health. In recent years the widespread use of antibiotics has led to an increase in the concentration of antibiotic-resistant bacteria also in natural environments. The study was conducted in bathing areas three recreational lakes located in the Zaborski Landscape Park in northern Poland. Water samples were collected in three parallel repetitions in April, June and September 2022. Our study indicates that anthropopressure connected with tourism and recreation promotes the growth of fecal bacteria, including antibiotic-resistant strains, whose significant accumulation was recorded in September, the month marking the end of summer vacation. Antibiotic resistance profiles showed that isolated strains of fecal bacteria were resistant to beta-lactam antibiotics. The highest percentage of Escherichia coli strains showed resistance to cefepime (39.1%), and enterococci to imipenem (26.9%). The amplification of resistance genes confirmed the presence of only selected bla genes in the examined strains of fecal bacteria. The blaTEM gene was found in 14 strains of Enterococcus faecium (82.4%), in all 4 isolates of Enterococcus faecalis, and in 4 out of 5 unspecified strains of fecal streptococci. In Escherichia coli only blaCTX gene was identified in one strain. The presence of blaTEM genes was strongly correlated with the concentration of fecal bacteria, it can therefore be assumed that the presence of resistance genes was caused by direct contamination of the studied lakes with feces containing antibiotic-resistant bacteria, presumably without contamination from other sources. Resistance genes found in the control strains from sewage treatment plants were not identified in the studied isolates. Antibiotic resistance genetic markers found in strains isolated from wastewater may prove helpful in determining the sources of contamination of natural aquatic ecosystems with antibiotic-resistant fecal bacteria and thus ensure efficient management of projects aimed at making these waterbodies available for public use.