Non-linear time series analysis of the impacts of national antibiotic stewardship and infection control strategies on MRSA infections in a region of Scotland

Abstract

This paper explores associations between antibiotic stewardship, infection control, and clinical burdens from methicillin-resistant Staphylococcus aureus (MRSA) with aretrospective ecological study and non-linear time-series analysis over Scottish HealthBoard. The participants are adult, non-obstetric, admissions to all hospitals (N=1,378,805)and registrations in primary care (455,008) between January 1997 and December 2012.The following interventions are considered: antibiotic stewardship limiting use of ‘4C’(cephalosporins, co-amoxiclav, clindamycin, fluoroquinolones) and macrolide antibiotics; hand-hygiene campaign; universal MRSA admission screening; hospital environmentinspections. The dependent variables are MRSA Prevalence density in hospital(cases/1000 occupied bed-days, OBDs) and community (cases/10,000 inhabitant-days,IDs)Our results demonstrate that during antibiotic stewardship use of ‘4C’ and macrolideantibiotics declined by 47% in hospitals and 29% in the community. In time-seriesanalyses for each hospital (R2 0.71 to 0.91) MRSA prevalence densities were: inverselyrelated to hand-hygiene, HIE, and admission screening; and positively associated with MRSA rates in other hospitals, importation pressures, bed-occupancy, and use of ‘4C’ ormacrolide antibiotics exceeding hospital-specific thresholds (lags 0-4 months).Community rates were predicted by: hospital MRSA (lags 1-4); and primary care use ofmacrolides, fluoroquinolones, and clindamycin (above thresholds of 2.82, 0.72 and 0.44DDDs/1,000 IDs). Combined interventions were associated with reductions in MRSA of51% in hospitals and 47% in the community. Declines associated with antibioticstewardship were 46% and 37%, respectively. Across all services 1159 MRSAinfections/year were prevented.The main conclusion of this paper is that antibiotic stewardship reduced population useof ‘4C’ and macrolide antibiotics to below thresholds for associations with MRSA, andalongside other national infection control strategies predicted rapid reductions in clinical burdens. Knowing thresholds in antibiotic use may be revealed one of the most importantissues to control resistant infections