Mupirocin and chlorhexidine resistance in Staphylococcus aureus in patients with community-onset skin and soft tissue infections

Abstract

Decolonization measures, including mupirocin and chlorhexidine, are often prescribed to prevent Staphylococcus aureus skin and soft tissue infections (SSTI). The objective of this study was to determine the prevalence of high-level mupirocin and chlorhexidine resistance in S. aureus strains recovered from patients with SSTI before and after mupirocin and chlorhexidine administration and to determine whether carriage of a mupirocin- or chlorhexidine-resistant strain at baseline precluded S. aureus eradication. We recruited 1,089 patients with community-onset SSTI with or without S. aureus colonization. In addition to routine care, 483 patients were enrolled in a decolonization trial: 408 received intranasal mupirocin (with or without antimicrobial baths), and 258 performed chlorhexidine body washes. Patients were followed for up to 12 months with repeat colonization cultures. All S. aureus isolates were tested for high-level mupirocin and chlorhexidine resistance. At baseline, 23/1,089 (2.1%) patients carried a mupirocin-resistant S. aureus strain and 10/1,089 (0.9%) patients carried chlorhexidine-resistant S. aureus. Of 4 patients prescribed mupirocin, who carried a mupirocin-resistant S. aureus strain at baseline, 100% remained colonized at 1 month compared to 44% of the 324 patients without mupirocin resistance at baseline (P = 0.041). Of 2 patients prescribed chlorhexidine, who carried a chlorhexidine-resistant S. aureus strain at baseline, 50% remained colonized at 1 month compared to 48% of the 209 patients without chlorhexidine resistance at baseline (P = 1.0). The overall prevalence of mupirocin and chlorhexidine resistance is low in S. aureus isolates recovered from outpatients, but eradication efforts were less successful in patients carrying a mupirocin-resistant S. aureus strain at baseline.

Fig 1

(A) Baseline and longitudinal carriage of mupirocin-resistant S. aureus strains stratified by randomization to perform mupirocin decolonization. Mup-R, mupirocin-resistant strain; Mup-S, mupirocin-susceptible strain. (B) Baseline and longitudinal carriage of chlorhexidine-resistant S. aureus strains stratified by randomization to perform chlorhexidine decolonization. Qac⁺, strain carrying the qacA/B genes and therefore classified as chlorhexidine resistant; Qac⁻, strain not carrying the qacA/B genes and classified as chlorhexidine susceptible.

Fig 2

(A) S. aureus colonization at the 1-month longitudinal sampling of patients prescribed mupirocin stratified by a mupirocin-resistant or -susceptible isolate at baseline. Mup-R, mupirocin-resistant strain; Mup-S, mupirocin-susceptible strain. (B) S. aureus colonization at the 1-month longitudinal sampling of patients prescribed chlorhexidine stratified by a chlorhexidine-resistant or -susceptible isolate at baseline. Qac⁺, strain carrying the qacA/B genes and therefore classified as chlorhexidine resistant; Qac⁻, strain not carrying the qacA/B genes and classified as chlorhexidine susceptible.