AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Detection of Tetracycline Resistance and Class 1 Integrase Genes in Indoor and Outdoor Air
ALISON L. LING, Mark T. Hernandez, Norman R. Pace, Timothy M. LaPara, University of Colorado
Abstract Number: 213 Working Group: The Indoor Microbiome
Abstract Antibiotic resistance genes are considered an emerging environmental contaminant. Of the possible transfer routes, airborne transmission of antibiotic resistance is the least understood, but may be a major pathway in indoor environments. Most studies of airborne microbes and their antibiotic resistance potential have been culture-based, which likely underestimates the abundance of airborne resistance genes.
This study verifies the presence of tetracycline resistance genes in both indoor and outdoor air using quantitative PCR to target two tetracycline resistance genes (tet(X) and tet(W)) and a class 1 integrase (intI1) gene, in conjunction with the bacterial 16S rRNA gene (a marker for total bacteria abundance). Aerosol samples were collected from potentially high exposure indoor environments (two livestock farms, two clinics, and a homeless shelter), as well as outdoor sites on Colorado’s Front Range (urban, agricultural and pristine). Gene copy abundance was normalized to volume of air sampled. Abundance of all genes observed were 10-100 times higher in confined animal feeding operations than in other environments, and tet(W) gene counts were typically 10-100 times higher than either tet(X) or intI1. The ratio of resistance genes to bacterial 16S genes was higher in the clinics and the homeless shelter than in the farms, indicating that a higher percent of airborne bacteria carry resistance potential in these environments. Genes encoding tet(W) were detected in outdoor air near livestock operations, and tet(X) and intI1 gene sequences were detected in air collected from a high alpine forest. Sequencing revealed a higher amount of variation in the gene sequences obtained for tet(W) and tet(X) genes (65% for both) than for intI1 genes (50%). These results indicate that antibiotic resistance and class 1 integrase genes can persist in both indoor and outdoor air, and suggest the possibility of both short-range and long-range atmospheric transport of antibiotic resistance potential.