|Blaustein, Ryan - University Of Maryland|
|Stocker, Matt - Orise Fellow|
|Van Kessel, Jo Ann|
Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: 5/7/2015
Publication Date: 5/20/2015
Citation: Blaustein, R., Shelton, D.R., Stocker, M., Pachepsky, Y.A., Van Kessel, J.S., Karns, J.S. 2015. Biofilm-induced changes in microbial quality of irrigation water: Indicator bacteria and antibiotic-resistance. BARC Poster Day. 26th Annual Beltsville Poster Day, National Agriculture Library on May 20, 2015.
Technical Abstract: Irrigation waters are implicated in the transmission of pathogens to fresh produce, and microbial release and retention from biofilms that form on inner surfaces of irrigation lines may impact the quality of delivered water. Biofilms in water distribution systems have been suggested as a reservoir for antibiotic-resistant bacteria and associated genes, but little is known about the role of biofilms in contributing to the dissemination of antibiotic resistance toward human exposure via irrigation systems. We conducted weekly 2 h irrigation events at the USDA-ARS South Farm research site for one month, using Paint Branch Creek as the water source. During the four irrigation events, concentrations of heterotrophic bacteria, total coliforms, fecal coliforms, and Escherichia coli, as well as concentrations of these bacterial groups/species that were resistant to ampicillin and tetracycline were monitored at the intake surface water and output sprinkler water. Prior to each of the latter three events, 15 cm sections of pipeline were removed and biofilm was scraped and analyzed for total protein content and all of the above bacteria; in addition, bacterial concentrations in residual pipe water were determined. Isolates of biofilm-associated bacteria were screened for resistance to a panel of 5 different antibiotics/antibiotic classes. Bacteria grew substantially in the residual water between irrigation events and biomass of the biofilm steadily increased from week to week. Probabilities varied from low to high that the concentrations of (antibiotic-resistant) bacteria were different at the system intake and outputs. The percentages of biofilm-associated bacteria that were resistant to each to the antibiotics/antibiotic classes varied and sometimes changed from week to week. Cases of multiple-resistance were seen for all bacterial groups/species, most often for fecal coliforms. The distribution patterns of multiple-resistance differed among bacterial groups/species and sometimes changed from week to week. These results indicate the potential for biofilms in irrigation systems to harbor and propagate antibiotic resistant bacteria and alter concentrations that are flowing through the system.