Seasonal changes in airborne fungi and bacteria at a dairy cattle concentrated animal feeding operation in the southwest United States.

The objective of this study was to evaluate a dairy located in the arid southwest United States to determine the concentrations and seasonal variation of airborne fungi and bacteria and to determine the percentage of antibiotic resistant Staphylococcus aureus. The authors used two-stage ambient air sampling systems to measure the culturable airborne fungal organisms and bacteria on a monthly basis. The authors recovered the most fungal, bacterial, and S. aureus organisms during the spring months. The most common fungi identified were Cladosporium, Aspergillus, and Stemphylium, which were most common in the spring and least common in the summer. S. aureus made up 4.2% to 5.5% of the total bacteria, and greater than 50% of this bacteria were found to be resistant to ampicillin, penicillin, or cefaclor, with the greatest incidence of antibiotic resistance occuring in the fall. The incidence of S. aureus resistant to at least two antibiotics ranged from 14% in the spring to 54% in the fall.