Success rates of decolonisation treatment and risk factors for chronic carriage in methicillin-resistant Staphylococcus aureus throat carriers: a retrospective population-based cohort study.

Background: Throat carriage of methicillin-resistant Staphylococcus aureus (MRSA) has previously been associated with lower decolonisation treatment success rates.

Objectives: To characterise decolonisation treatment and outcome in Danish MRSA throat carriers.

Methods: This retrospective population-based cohort study included MRSA throat carriers between July, 2018 and June, 2019, in the Capital Region of Denmark. Logistic regression analysis was performed to assess variables associated with becoming MRSA free.

Results: Of 178 patients included, 129 (72%) were MRSA free by the end of the study. Overall, 78 (44%) of patients became MRSA free following a treatment attempt. Twenty-six (15%) patients became MRSA free without treatment and 25 (14%) became MRSA free unrelated to a treatment attempt. The success rate of the first decolonisation treatment, mainly nasal mupirocin and chlorhexidine body wash, was 23%. Systemic clindamycin was given in 52 cases and had a success rate of 52%. Logistic regression showed that residing in a household with three to four additional MRSA carriers was negatively associated with becoming MRSA free, although not significant after adjustment. Having MRSA in a clinical sample prior to decolonisation was associated with a lower chance of becoming MRSA free after adjustment. Topical decolonisation treatment was associated with a lower probability of becoming MRSA free.

Conclusion: In this Danish cohort of MRSA throat carriers, the overall success rate of decolonisation treatment was 44% and for systemic clindamycin 52%. A higher number of household MRSA carriers and a previous clinical MRSA infection were associated with a lower chance of becoming MRSA free.