MRSA colonization. Aspects on epidemiology and treatment

Methicillin-resistant Staphylococcus aureus, MRSA, has become a common pathogen within healthcare facilities and the community and is a major challenge to the treatment of S. aureus infections. In Sweden the prevalance is still low with less than 1 % MRSA among S. aureus in blood cultures in 2014, but an increasing proportion of cases in the community is noted. In 2011 a novel mecA gene homologue, mecC, was reported. In this thesis different aspects of MRSA colonization is studied in order to create a greater understanding on how patients with MRSA should best be dealt with and treated in healthcare. The overall objective is preventing the spread of MRSA. The duration of MRSA colonization and factors influencing the duration of MRSA colonization. The median duration of MRSA colonization was 5.9 months. Having household contacts with MRSA, young age, spa-type t002 and colonization in 2 or more locations, was significantly associated with a longer duration of colonization. Having a clinical infection treated with antibiotics was signi ficantly associated with a shorter time of carriage. Eradication treatment was associated with a shorter carriage time. These results may have implications for the management of patients with MRSA carriage. The study indicates that MRSA carriage can be defined as ‘ negative ’ in a follow-up program and thereby be freed from control measures in health care. The results also shows the importance of performing contact tracing among household members in MRSA follow-up programs. The epidemiology of different MRSA spa-types in Skåne County There was a change in the epidemiology of MRSA in Skåne County during the study period with a ten-fold increase from 2000 to 2010. There was a strong association between MRSA acquisition and either a non-Swedish origin or travelling and staying abroad. Different spa types were seen in patients who had travelled to or originated from different regions of the world.The PVL-positive strains with spa-types t008, t019 or t044 caused significantly more skin infections compared to the other spa-types. In our study, 35% of the screened household contacts were positive for MRSA with none of the spa-types being significantly more prone to spread. Our results supports screening for MRSA in patients treated in health-care settings abroad and taking cultures from patients with skin infections contracted outside Sweden. It also supports continued contact tracing of household contacts. Knowledge of the spa-type may give valuable clues in the process of contact tracing Eradication of MRSA colonization in the throat MRSA colonization in the throat is possible to eradicate. Our study shows that topical treatment is not sufficient to eradicate MRSA carriage in the throat and that addition of systemic treatment substantially increases the success rate. The epidemiology of mecC MRSA in Skåne County MecC MRSA mainly affects older patients with underlying diseases or with an existing skin lesion. The mecC MRSA in our region appears to have a domestic origin. Data indicates that it could be a poor colonizer with few secondary cases and few people being colonized for a long time It is important and worthwhile with interventions to prevent the spread of MRSA. The interventions have to be continously evaluated in relation to the prevalence of MRSA in the community. General measures with basic hygiene precautions and environmental cleaning, is and will be of even more importance in limiting spread of MRSA in health care.