Presence of Multidrug-Resistant E. coli, Enterococcus spp. and Salmonella spp. in Lakes and Fountains of Porto, Portugal

Urban lakes and fountains provide recreational activities that could facilitate the contact between humans, animals and biological agents. The objective of this work was to assess the water quality and safety of 17 lakes and 13 fountains in the city of Porto (Portugal), by detecting the presence of Escherichia coli, enterococci and Salmonella spp., and analyzing their antimicrobial resistance. The mean number of E. coli colony forming units (CFU) was higher, both in lakes (2.67 × 10 CFU/100 ml) and fountains (3.52 × 10 CFU/100 ml), in comparison to enterococci counts: 5.60 × 10 and 4.10 × 10 CFU/100 ml, respectively. By screening a set of 26 multidrug-resistant E. coli (including seven ESBL-producing isolates) for virulence genes, we found strains carrying the fimH, chuA, cvaC, cnf1, hlyA, TSPE4.C2 and yjaA genes. Phylogenetic analyses have shown that the majority of E. coli strains belong to groups A and B1. Salmonella spp. was found in two lake water samples. Generally, the fecal contamination was notorious and worrisome, requiring preventive measures to minimize the negative impacts on human health. Finding the contamination source is definitely important so that interventions can be more effective.