VIABLE ANTIBIOTIC-RESISTANT BACTERIA ARE DISSEMINATED ON AIRBORNE PARTICULATE MATTER FROM CATTLE FEED YARDS
Loren Hensley, Kimberly Wooten, Phil Smith, Gregory D. Mayer.
Texas Tech University, Lubbock, TX.
Increasing incidence of antibiotic resistance is cause for concern because, without effective antibiotics, humans could quickly lose the war on bacterial disease. Antibiotic-resistant bacteria are generated in settings where antibiotics are used in large quantities, such as hospitals, veterinary clinics, and animal production facilities. Some estimates suggest that the amount of antibiotics used in animal production industries constitutes as much as 80% of total North American antibiotic usage. Recently, our group described aerial dissemination of antibiotics, bacteria, and antibiotic-resistant genes on airborne particulate matter emanating from cattle feedlots. Because the previous study used a sequencing approach, results were unable to confirm viability of the fugitive bacteria. Given the robust population diversity observed in the previous study, we hypothesized that particulate matter could harbor viable bacteria, and that members of this population would exhibit antibiotic resistance. Here we show that numerous bacteria associated with feedlot particulate matter are indeed viable in laboratory culture, including several isolates that are antibiotic resistant. Particulate matter samples isolated on sterile filters placed downwind of feed yards were cultured in Luria broth and tripticase soy broth, both with and without tetracycline at 50 µg/ml. Viable bacteria included a subset of those observed by sequencing. Tetracycline-resistant isolates were observed on tripticase soy agar plates using the disc diffusion method. Isolates were identified by sequencing of the 16S rRNA gene variable regions 1-3. This study validates previous sequencing-based investigations and provides proof of principle that viable antibiotic-resistant bacteria are emitted from feedlots via airborne particulate matter.