Strain relatedness in 66 pairs of repeated MRSA infection episodes, categorized according to PFGE types of preceding isolates and intervals.

PFGE, pulsed-field gel electrophoresis.1One child had 3 infection pairs caused respectively by indistinguishable strains (2 pairs) and highly related strains (1 pair).2The rate of paired infections caused by indistinguishable strains was higher for PFGE type D (carrying Panton-Valentine leukocidin genes) than for other PFGE types (P = 0.007, Fisher's exact test).3Strain relatedness was not associated with the length of intervals (indistinguishable strains vs. highly related or distinct strains, p = 0.404).