Transmission through air as a possible route of exposure for MRSA

Abstract

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is highly prevalent in pigs and veal calves. The environment and air in pig and veal calf barns is often contaminated with LA-MRSA, and can act as a transmission source for humans. This study explores exposure-response relationships between sequence type 398 (ST398) MRSA air exposure level and nasal ST398 MRSA carriage in people working and/or living on farms. Samples and data were used from three longitudinal field studies in pig and veal calf farm populations. Samples consisted of nasal swabs from the human participants and electrostatic dust fall collectors capturing airborne settled dust in barns. In both multivariate and mutually adjusted analyses, a strong association was found between nasal ST398 MRSA carriage in people working in the barns for >20 h per week and MRSA air levels. In people working in the barns < 20 h per week there was a strong association between nasal carriage and number of working hours. Exposure to ST398 MRSA in barn air seems to be an important determinant for nasal carriage, especially in the highly exposed group of farmers, next to duration of contact with animals. Intervention measures should therefore probably also target reduction of ST398 MRSA air levels.

Increased risk of pneumonia in residents living near poultry farms: does the upper respiratory tract microbiota play a role?

“…This is in contrast to a Finnish study [39], which observed that environmental biodiversity was associated with a higher generic diversity of skin gammaproteobacteria, presumably resulting from direct contact with environmental microbiota. Although there is some evidence that transmission of farm-related bacteria may take place through air—for example, in pig and veal calf farmers and their family members, nasal colonization by livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) occurs frequently [40]—we did not find evidence of zoonotic infections explaining the increased risk of CAP around poultry farms [9]. …”

Staphylococcus aureus Nasal Colonization Differs among Pig Lineages and Is Associated with the Presence of Other Staphylococcal Species

“…As S. aureus is transmitted via direct contact and through dust, it may be assumed that this organism is present throughout the entire farm and all pigs are exposed to this organism (17). Despite this general exposure, S. aureus was only detected in 65% of the animals.…”

“…It was shown that for pig farmers the most important determinants for becoming an MRSA carrier are the exposure to high amounts of MRSA in the air of the barn and the hours that are spent in the barn (17). That study did not find an association between MRSA persistence in farmers and the proportion of MRSA-positive animals on the farm.…”

Impacts of Intensive Livestock Production on Human Health in Densely Populated Regions

“…In the past decade, a specific clone of methicillin‐resistant Staphylococcus aureus (MRSA), referred to as livestock‐associated MRSA (LA‐MRSA) has emerged in livestock and people in direct contact with livestock, in particular, pigs and veal calves (Graveland et al, ; Voss et al, ). Although airborne transmission is a likely route of exposure in farmers (Bos et al, ), it is unclear whether LA‐MRSA is transmitted to nonfarming residents through the environment, for example, by air. In a large population survey, only 10 out of 2,492 Dutch adults carried LA‐MRSA, but carriers lived closer to a livestock farm than noncarriers, a difference that remained statistically significant after adjustment for farm animal contact (Zomer, Wielders, et al, ).…”