Abstract
Aerosolized methicillin-resistant Staphylococcus aureus (MRSA) was sampled inside and downwind of a swine facility. Animal feed was sampled before and after entry into the swine facility. Aerosolized particles were detected using an optical particle counter for real time measurement and with an Andersen Sampler to detect viable MRSA. Molecular typing and antimicrobial susceptibility testing were performed on samples collected. Viable MRSA organisms isolated inside the swine facility were primarily associated with particles > 5µm, and those isolated downwind from the swine facility were associated with particles <5µm. MRSA isolates included spa types t008, t034, and t5706 and were resistant to methicillin, tetracycline, clindamycin, and erythromycin. Animal feed both before and after entry into the swine facility tested positive for viable MRSA. These isolates were of similar spa types as the airborne MRSA organisms. Air samples collected after power washing with a biocide inside the swine facility resulted in no viable MRSA organisms detected. Our pilot study showed that the ecology of MRSA is complex. Additional studies are warranted on the maximum distance that viable MRSA can be emitted outside the facility, and the possibility that animal feed may be a source of contamination.
Generated Summary
This pilot study investigated the detection of airborne methicillin-resistant Staphylococcus aureus (MRSA) inside and downwind of a swine facility, along with the presence of MRSA in animal feed. The study aimed to assess the potential for occupational, animal health, and environmental implications related to MRSA transmission in swine production settings. The research employed an Andersen Sampler and an Optical Particle Counter to detect viable MRSA and measure particle sizes. Molecular typing and antimicrobial susceptibility testing were conducted on collected samples. The study also examined the effect of power washing with a biocide on the presence of airborne MRSA. The methodology involved sampling air and animal feed, followed by laboratory analysis to identify MRSA strains and their characteristics. The scope of the study was limited to one swine farm, focusing on understanding the ecology of MRSA and potential sources of contamination within and around swine facilities. The research was conducted during the fall season over a few days.
Key Findings & Statistics
- The median particle count for particles (> 5µm) inside the facility was 1particles/m³ (range = 0.106-3.095 p/ m³), and for outside downwind of the facility a median of 0.006 p/ m³ (range=0-6.238 p/ m³) was measured.
- The median particle count for particles (<5 µm) inside the facility was 2.470 p/ m³ (range=1.170-1,119.093 p/ m³), and for downwind the facility a median of 0.363 p/ m³ (range=0-42.738 p/ m³) was measured.
- Viable sampling using the Andersen Sampler showed that the particles (<5um) inside the swine facility ranged from 11.6 × 10³ cfu/m³ to 15.9 ×10³ cfu/m³ with the mean of 13.8 cfu/m³.
- Downwind of the facility the concentration of viable total particles (<5 um) ranged from 15 cfu/m³ to 111 cfu/m³, with the mean of 63 cfu/m³.
- MRSA particles (> 5um) inside the swine facility ranged from 547 cfu/m³ to 1,103 cfu/m³; the mean concentration was 825 cfu/m³.
- MRSA particles (<5 um) inside the swine facility ranged from74 cfu/m³ to 302 cfu/m³; the mean concentration was 188 cfu/m³.
- Downwind of the facility, MRSA particles (<5 um) were detected with the mean concentration of 5 cfu/m³.
- Twelve isolates (100%) were resistant to methicillin; eight of twelve (67%) were resistant to tetracycline and clindamycin; and four of twelve (33%) were resistant to erythromycin.
- Animal feed from both the truck and inside the swine facility tested were resistant to methicillin (4/4) and erythromycin (4/4).
Other Important Findings
- MRSA was detected inside the swine facility and downwind, indicating potential for airborne transmission.
- MRSA isolates included spa types t008, t034, and t5706 and were resistant to methicillin, tetracycline, clindamycin, and erythromycin.
- Animal feed tested positive for viable MRSA both before and after entry into the swine facility.
- Air samples collected after power washing with a biocide inside the swine facility resulted in no viable MRSA organisms detected.
- MRSA in the air was associated with different particle sizes: >5µm inside the facility and <5µm downwind.
- The study identified that the MRSA spa type t034 was present in the animal feed, air samples inside and downwind the CAFO.
Limitations Noted in the Document
- The study was conducted on a single swine farm, limiting the generalizability of the results.
- The pilot study did not account for factors such as the age and size of the pigs, the time of day for sampling, and ventilation rates.
- Sampling was conducted over a few days during the fall season, which may not represent year-round conditions.
- The study’s observational nature and lack of intervention studies limit the conclusions about the effectiveness of power washing and disinfecting.
Conclusion
The findings of this pilot study underscore the complexity of MRSA ecology within swine facilities and the potential for its airborne transmission. The detection of MRSA both inside and downwind of the facility, along with its presence in animal feed, highlights multiple pathways for exposure and spread. The study’s results suggest that the source of MRSA and contamination may be complex. The identification of specific spa types in both air and feed further supports the idea that animal feed may be a source of MRSA at the facility. The study’s findings are consistent with other research indicating airborne MRSA in and around swine facilities. The ability of the study to detect MRSA at a greater distance than previously reported suggests that the potential for airborne transmission is a significant consideration. The study’s results are a reminder that further research is warranted to determine the full extent of airborne MRSA transmission from swine facilities. Further investigation is needed to evaluate animal feed as an additional source of MRSA in swine barns. Future studies should focus on the maximum distance that viable MRSA can be emitted outside the facility and the effectiveness of various intervention strategies, such as power washing and disinfection, in controlling MRSA transmission. The study’s findings reinforce the need for a comprehensive approach to mitigate the risks associated with MRSA in swine production, including the implementation of effective biosecurity measures and regular monitoring of air and feed for MRSA contamination. In conclusion, this study has provided some interesting insights into MRSA and its transmission in swine facilities and has provided a roadmap for future study of this topic. The study revealed the potential for feed contamination, and transmission further from the swine facilities than was previously known. Therefore, more studies are needed for this important field.