High prevalence of multidrug-resistant Escherichia coli and Enterococcus spp. in river water, upstream and downstream of a wastewater treatment plant

• Published in: Journal of water and health Vol. 12; no. 3; pp. 426 - 435
• Main Authors: Bessa, Lucinda J, Barbosa-Vasconcelos, Ana, Mendes, Angelo, Vaz-Pires, Paulo, Martins da Costa, Paulo
• Format: Journal Article
• Language: English
• Published: England IWA Publishing 01.09.2014
• Subjects: Anti-Bacterial Agents - pharmacology; Antibiotics; Antiinfectives and antibacterials; Antimicrobial agents; Antimicrobial resistance; Azithromycin; Bacteria; Colony Count, Microbial; Downstream; Drug resistance; Drug Resistance, Multiple, Bacterial; Drugs; E coli; Enterococcus; Enterococcus - drug effects; Enterococcus - genetics; Enterococcus - isolation & purification; Enumeration; Environmental Monitoring; Erythromycin; Escherichia coli; Escherichia coli - drug effects; Escherichia coli - genetics; Escherichia coli - isolation & purification; Freshwater; Imipenem; Microbial Sensitivity Tests; Microorganisms; Multidrug resistance; Multidrug resistant organisms; Multiplex Polymerase Chain Reaction; Phenotypes; Portugal; Prevalence; Profiles; Rifampin; River water; Rivers; Rivers - microbiology; Upstream; Vancomycin; Waste Disposal, Fluid; Wastewater; Wastewater treatment; Wastewater treatment plants; Water analysis; Water Microbiology; Water sampling; Water treatment; Portugal
• ISSN: 1477-8920; 1996-7829
• DOI: 10.2166/wh.2014.160

In this study, microbial quality and antimicrobial resistance of faecal bacteria from a Portuguese river were assessed. River water samples collected upstream and downstream of a wastewater treatment plant, throughout a 3-month period, were used for the enumeration of Escherichia coli and Enterococcus spp. The highest numbers found for E. coli and enterococci were 1.1 × 10⁴ and 1.2 × 10⁴ colony forming units (CFU)/100 ml, respectively. In total, 144 isolates of E. coli and 144 of enterococci were recovered and tested for antimicrobial susceptibility; 104 E. coli and 78 Enterococcus spp. showed resistance to one or more antimicrobial drugs. Overall, 70 and 32 different resistance patterns were found for E. coli and enterococci, respectively. One E. coli showed resistance to imipenem and 29 isolates were extended spectrum β-lactamase-producers. Multidrug-resistant E. coli belonged mostly to groups A, B1 and group D. Enterococcus spp. were mostly resistant to rifampicin, tetracycline, azithromycin and erythromycin; six isolates showed resistance to vancomycin, presenting the VanA phenotype. The high levels of E. coli and enterococci and the remarkable variety of antimicrobial resistance profiles, reinforces the theory that these river waters can be a pool of antimicrobial resistance determinants, which can be easily spread among different bacteria and reach other environments and hosts.