Experimental nasal colonization of piglets with methicillin-susceptible and methicillin-resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus sequence type (ST)398 is widely spread among livestock. People in contact with livestock have a higher risk of testing positive for MRSA. Several experimental settings have been described to study in vivo colonization of MRSA in pigs, each having its own limitations. The aim of this study was to develop a nose-colonization model in pigs to quantitatively study the colonization of MRSA and the co-colonization of MSSA and MRSA. Two experiments were performed: in the first experiment piglets received an intranasal inoculation with MRSA ST398, spa-type t011, and in the second experiment piglets received an intranasal inoculation with two MSSA strains (ST398, spa-type t011 and t034) and two MRSA strains (also ST398, spa-type t011 and t034) to investigate co-colonization. Colonization was quantitatively monitored for 2 weeks in both experiments. Nasal colonization was successfully established in all piglets with stable numbers of S. aureus between 10(4) and 10(6) CFU. MSSA and MRSA were able to co-colonize.