Variations in spa types found in consecutive MRSA isolates from the same patients.

Very little is known about how the spa gene mutates over time in methicillin-resistant Staphylococcus aureus (MRSA) from the same patient. Copenhagen is an area with low prevalence of MRSA but with high variability in spa types. We collected 1536 MRSA isolates from 319 patients during a 5-year period and found spa type alterations in 30 MRSA isolates (2%) from 13 patients (4%). The alteration most often seen was the deletion of repeats followed by repeat duplication and point mutation.