Irrigation workers' exposures to antimicrobial-resistant bacteria and antimicrobials present in reclaimed wastewater

As water shortages become more common, reclaimed wastewater is increasingly being used for irrigation activities. Because of this practice, workers conducting spray irrigation could be exposed to antibiotic-resistant bacteria and antimicrobials that may remain in treated wastewater. We are initiating a study to evaluate the presence of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus spp. (VRE), and antimicrobial residues in reclaimed wastewater used for spray irrigation. Our study will also evaluate potential inhalation and dermal exposures to these agents among spray irrigation workers. Our hypothesis is that reclaimed wastewater may contain MRSA, VRE, and antimicrobial residues and that spray irrigation workers could be exposed to these agents via multiple routes of exposure. We will sample reclaimed wastewater, air, dermal, and nasal swab samples at sites in Maryland and Nebraska. We will evaluate the presence of MRSA and VRE and quantify the number of organisms in each sample using standard membrane filtration methods and direct plating techniques. Vancomycin-amended Enterococcosel agar and oxacillin-amended Baird Parker agar will be used to culture VRE and MRSA, respectively. Antimicrobial residues will be analyzed using an isotope dilution liquid chromatography tandem mass spectrometry method. Although previous studies have analyzed MRSA in clinical settings and VRE in aquatic environments, no studies have quantified the prevalence of MRSA, VRE, and antimicrobials in reclaimed wastewater and biological samples collected from spray irrigation workers. Our findings will be important in assessing possible microbial and chemical risks from using reclaimed wastewater, which is likely to become a more common water source.