Increasing trend in fusidic acid resistance among MRSA isolates in the Netherlands, 2016-2023

SynopsisO_ST_ABSObjectivesC_ST_ABSRecently, several methicillin-resistant Staphylococcus aureus (MRSA) community outbreaks occurred in the Netherlands, including one caused by an impetigo-causing MRSA strain resistant to fusidic acid. Since fusidic acid and flucloxacillin are the main treatment options for impetigo, increasing resistance limits treatment possibilities. We examined trends in fusidic acid resistance levels among MRSA isolates in the Netherlands. MethodsData on routine bacteriological cultures between 2016-2023 from 30 laboratories were extracted from the national surveillance system on antimicrobial resistance (ISIS-AR). Fusidic acid resistance rates per year were calculated both overall and per age group for all MRSA isolates, and more specific, for the subset of MRSA isolates from wound/pus/skin samples collected by general practitioners (WPS-GP-samples). Trends were determined using logistic regression and compared with trends among methicillin-susceptible S. aureus (MSSA) isolates. ResultsWe found an increasing trend in fusidic acid resistance among MRSA isolates from 15% in 2016 to 30% in 2023 (p<0.001) which differed significantly from the trend among MSSA isolates (p<0.001). An increase was also found in MRSA WPS-GP-samples, both among young children and the population of 13-64 years old, but not among elderly. The trends remained significant after exclusion of isolates associated with known fusidic acid-resistant MRSA outbreaks, both among MRSA isolates overall (OR = 1.10, 95% CI: 1.07-1.14, p<0.001) and among MRSA WPS-GP-samples (OR = 1.14, 1.07-1.21, p<0.001). ConclusionsIn conclusion, an increasing trend in fusidic acid resistance was found among MRSA isolates. Since impaired treatment for impetigo might ease the spread of (fusidic acid-resistant) MRSA, extra vigilance is warranted.