Theoretical modelling of LA-MRSA in Swedish pig production

Sammanfattning: Antimicrobial resistance is a threat to global health. Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is a category of multiresistant bacteria that primarily colonises livestock animals. While pigs are considered its main reservoir, LA-MRSA is zoonotic and causes an occupational risk to those working with livestock. However, LA-MRSA is also capable of spreading to humans without livestock contact. Although LA-MRSA carriers are usually asymptomatic, LA-MRSA can cause a wide range of infections in humans.The aim of this thesis was to use disease modelling to study the spread of LAMRSA and assess possible control strategies in a Swedish farrow-to-finish pig herd—additionally, the thesis aimed to fill knowledge gaps regarding the survival of LA-MRSA in the farm environment.The modelling studies concluded that eradicating LA-MRSA is challenging. Early detection and introduction of control measures were considerably more effective in lowering the within-herd prevalence than measures that were implemented when LA-MRSA had become established in the herd. The time to disease elimination was at least 300 days even with the most effective control measures that were introduced early at the outbreak phase of disease spread.In an experimental study, the survival of LA-MRSA strains belonging to the clonal complex (CC) 398 varied on different surface materials (concrete, polypropylene plastic and stainless steel). This finding can be beneficial when planning efficient cleaning and disinfection routines in pig farms.In conclusion, investing in early detection and intensive early control measures may be justified if a low LA-MRSA prevalence country aims to have LA-MRSAfree pig herds.