Concentration of airborne Staphylococcus aureus (MRSA and MSSA) in pig farms

The aim of this study was to assess the potential occupational risk of working with Staphylococcus aureus-colonized pigs in Switzerland.

During the study it was estimated the airborne contamination by S. aureus in 37 pig farms (20 nursery and 17 fattening units; 25 in summer, 12 in winter). Quantification of total airborne bacterial DNA, airborne Staphylococcus sp. DNA, fungi, and airborne endotoxins was also performed.

In this experiment, the presence of cultivable airborne methicillin-resistant S. aureus (MRSA) CC398 in a pig farm in Switzerland was reported for the first time. Airborne methicillin-sensitive S. aureus (MSSA) was found in ~30% of farms. The average airborne concentration of DNA copy number of total bacteria and Staphylococcus sp. measured by quantitative polymerase chain reaction was very high, respectively reaching values of 75 (± 28) × 10⁷ and 35 (± 9.8) × 10⁵ copy numbers/m³ in summer and 96 (± 19) × 10⁸ and 40 (± 12) × 10⁶ copy numbers m–3 in winter. Total mean airborne concentrations of endotoxins (1298 units of endotoxin/m³) and fungi (5707 colony-forming units/m³) exceeded the Swiss recommended values and were higher in winter than in summer.

In conclusion, Swiss pig farmers will have to tackle a new emerging occupational risk, which could also have a strong impact on public health. The need to inform pig farmers about biological occupational risks is therefore crucial.