Fusidic Acid-resistant Staphylococcus aureus in Impetigo Contagiosa and Secondarily Infected Atopic Dermatitis

Fusidic acid-resistant Staphylococcus aureus (FRSA) has been identified as a causative agent in outbreaks of impetigo and its emergence has been associated with increased use of topical fusidic acid. The frequency of FRSA in atopic dermatitis (AD) has been less extensively investigated. The aim of this study was to investigate the bacterial spectrum and frequency of FRSA in patients with impetigo or secondarily infected AD. A prospective study in our clinic in 2004 to 2008 included 38 patients with impetigo and 37 with secondarily infected AD. S. aureus was the predominant finding in all groups (bullous impetigo 92% (12/13), impetigo 76% (19/25) and secondarily infected AD 89% (33/37)). Seventy-five percent of S. aureus were fusidic acid resistant in bullous impetigo, 32% in impetigo and 6.1% in secondarily infected AD (bullous impetigo vs. AD p<0.0001, impetigo vs. AD p<0.05). We then performed a retrospective patient record review including all patients with impetigo or secondarily infected AD seen at the clinic during the first and last year of the prospective study. In the first year 33% (19/58) of the S. aureus isolates were fusidic acid-resistant in impetigo and 12% (5/43) in secondarily infected AD (p<0.05). In the last year corresponding values were 24% (6/25) for impetigo and 2.2% (1/45) for AD (p<0.01). In summary, the prospective study and the patient record review both showed higher FRSA levels in impetigo than in AD. FRSA levels were persistently low in AD. Continued restrictive use of topical fusidic acid is advised to limit an increase in FRSA levels in dermatology patients.