Preventive Effect of Nasal Lavage with Physiologic Saline on the Colonization with MRSA after Working in Porcine Stable

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) are common colonizers of the anterior nares of healthy pigs and pig-workers (farmers, veterinarians or researchers). This potential of zoonotic spread constitutes a serious health risk for both – humans and animals. Researchers working in pig stables were continuously monitored for their MRSA colonization and the probability to leave the stable after working 3 to 6 h with a positive finding were between 30 and 60 %. The aim of the study was to identify easy-appreciable prevention procedures that might reduce the risk of MRSA transmission from pigs and stable environment to humans, who are working in pig stables only for a short-time period. A prestudy was performed, where surgical masks failed to have any protection effect on colonization with MRSA (n=3) in pig herds with high occurrence of MRSA (> 80%). Nasal swab samples were taken from subjects (n=40, researchers and students) who were working with pigs for 4 to 6 h and analyzed for MRSA by plating onto selective chromogenic MRSA agar, followed by inoculation on Columbia blood agar and processed through MALDI-TOF MicroFlex platform. Sampling was performed before (T0), directly after working with pigs (T1) and after nasal lavage with saline solution (100ml of 0.9% NaCl each side, T3). Occurrence of MRSA in the pig herd was determined by nasal swaps of indicator pigs (n >10/ herd), dust sampling from surfaces (n=2/ herd) and in air samples (n=1/ herd). Significant differences were determined with the Mann-Whitney U test using SAS. None of the subjects were colonized with MRSA before, but 22.5 % directly after exposure to pigs and stable environment. MRSA colonization of the human subjects tended to be dependent on the proportion of positive MRSA findings in the pigs (P = 0.09), but up to now not related to air or dust (P > 0.3). None of the subjects were positive for MRSA after nasal lavage. Our results indicate that nasal lavage with physiologic saline solution can minimize the risk of MRSA colonization after working in porcine stable. The study is still ongoing to increase number of observations.