Prevalence of Staphylococcus aureus toxins and nasal carriage in furuncles and impetigo

The precise role of Staphylococcus aureus toxins and nasal carriage in common skin infections remains unclear. To seek correlations between toxin expression, S. aureus nasal carriage and clinical manifestations in patients with community-acquired furuncles and impetigo. From November 2004 to August 2005, we studied clinical data and bacteriological samples prospectively collected from 121 patients presenting with furuncles or impetigo. Sixty-four patients (31 with furuncles and 33 with impetigo) had S. aureus-positive skin culture. Panton-Valentine leukocidin (PVL) genes were present in 13 of 31 (42%) isolates from furuncles and were associated with epidemic furunculosis. Exfoliative toxin genes were present in 10 of 10 (100%) and 12 of 21 (57%) bullous and nonbullous impetigo isolates, respectively. Nasal carriage of S. aureus was found in 58% of patients overall. It was strongly associated with chronic furunculosis but not with simple furuncles (88% vs. 29%, P < 0.007). Skin and nose isolates from a given patient always had identical characteristics. Methicillin-resistant S. aureus accounted for four of 64 (6%) positive skin cultures. PVL is not involved in all types of furuncles but is associated with epidemic furunculosis. Both bullous and nonbullous forms of impetigo are associated with exfoliative toxins. Staphylococcus aureus nasal carriage is associated with the chronicity of furuncles.