Occurrence of vancomycin-resistant and -susceptible Enterococcus spp. in reclaimed water used for spray irrigation

• Published in: Environmental research Vol. 147; pp. 350 - 355
• Main Authors: Carey, Stephanie Ann, Goldstein, Rachel E. Rosenberg, Gibbs, Shawn G., Claye, Emma, He, Xin, Sapkota, Amy R.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 01.05.2016
• Subjects: Agricultural Irrigation; Antibiotic-resistant bacteria; Antiinfectives and antibacterials; BACTERIA; Enterococci; Enterococcus; Enterococcus - isolation & purification; Enterococcus - physiology; Enterococcus faecalis; ENVIRONMENTAL SCIENCES; FRESH WATER; Irrigation; Microbial Sensitivity Tests; PENICILLIN; Reclaimed water; Reclamation; Recycling; Spray irrigation; Sprayers; Sprays; TETRACYCLINES; ULTRAVIOLET RADIATION; United States; Vancomycin Resistance; Vancomycin-resistant enterococci; WASTE WATER; Wastewater; Water quality; Water reclamation; WATER TREATMENT; United States; Antibiotic-resistant bacteria; Reclaimed water; Wastewater; Spray irrigation; Enterococci; Vancomycin-resistant enterococci
• ISSN: 0013-9351; 1096-0953
• DOI: 10.1016/j.envres.2016.02.030

Reclaiming municipal wastewater for agricultural, environmental, and industrial purposes is increasing in the United States to combat dwindling freshwater supplies. However, there is a lack of data regarding the microbial quality of reclaimed water. In particular, no previous studies have evaluated the occurrence of vancomycin-resistant enterococci (VRE) in reclaimed water used at spray irrigation sites in the United States. To address this knowledge gap, we investigated the occurrence, concentration, and antimicrobial resistance patterns of VRE and vancomycin-susceptible enterococci at three U.S. spray irrigation sites that use reclaimed water. We collected 48 reclaimed water samples from one Mid-Atlantic and two Midwest spray irrigation sites, as well as their respective wastewater treatment plants, in 2009 and 2010. Samples were analyzed for total enterococci and VRE using standard membrane filtration. Isolates were purified and then confirmed using biochemical tests and PCR. Antimicrobial susceptibility testing was conducted using the Sensititre® microbroth dilution system. Data were analyzed by two-sample proportion tests and one-way analysis of variance. We detected total enterococci and VRE in 71% (34/48) and 4% (2/48) of reclaimed water samples, respectively. Enterococcus faecalis was the most common species identified. At the Mid-Atlantic spray irrigation site, UV radiation decreased total enterococci to undetectable levels; however, subsequent storage in an open-air pond at this site resulted in increased concentrations of enterococci. E. faecalis isolates recovered from the Mid-Atlantic spray irrigation site expressed intrinsic resistance to quinupristin/dalfopristin; however, non-E. faecalis isolates expressed resistance to quinupristin/dalfopristin (52% of isolates), vancomycin (4%), tetracycline (13%), penicillin (4%) and ciprofloxacin (17%). Our findings show that VRE are present in low numbers in reclaimed water at point-of-use at the sampled spray irrigation sites; however, resistance to other antimicrobial classes is more prevalent, particularly among non-E. faecalis isolates. •Enterococci were recovered in 71% of reclaimed water samples.•Vancomycin-resistant enterococci were detected in 4% of reclaimed water samples.•UV radiation at irrigation sites reduced enterococci to undetectable levels.•Storage of reclaimed water in open-air ponds increased levels of enterococci.