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Dupilumab Sustains Long-Term Reduction of Staphylococcus aureus in Patients with Atopic Dermatitis
RAD 2025: Researchers observed a marked reduction and low burden of viable S. aureus on lesional and non-lesional skin after 1 year of dupilumab treatment.
Erica Anderson, MS
Photo courtesy of Vanderbilt University Medical Center
A new case series presented at the 2025 Revolutionizing Atopic Dermatitis (RAD) Conference shows that dupilumab therapy leads to sustained reductions in Staphylococcus aureus (S. aureus) colonization in both lesional and non-lesional skin of patients with atopic dermatitis (AD) after 1year of treatment. The microbial reductions were observed alongside clinically meaningful improvements in disease severity, supporting the long-term efficacy of interleukin (IL)-4 and IL-13 blockade in AD, researchers reported.
“Blockade of IL-13+/- IL-4 has been shown to result in rapid (< 2 weeks) and robust reduction in S. aureus skin abundance. We extend this observation by showing that this reduction in viable S. aureus on AD L and NL skin persists after at least one year of dupilumab treatment and was associated with clinical improvement,” investigators wrote in the study abstract.
The study, conducted at the University of Rochester Medical Center, evaluated 5 patients with moderate-to-severe AD enrolled in a longitudinal observational trial. All participants were colonized with viable S. aureus at baseline, with lesional bacterial counts ranging from 3 813 to 115 000 CFU/cm² and non-lesional counts from 3 to 48 750 CFU/cm².
After 12 to 18 months of continuous dupilumab therapy, S. aureus abundance was undetectable in 4 of 5 participants (80%) at both lesional and non-lesional sites. In the remaining participant—who had the highest initial burden—counts were reduced by several orders of magnitude to 48 CFU/cm² (lesional) and 2 CFU/cm² (non-lesional), accompanied by a drop in Eczema Area and Severity Index (EASI) from 15.2 to 6.6.
All participants experienced at least a 7-point reduction in EASI score (median [IQR]: 9.8 [8.0, 20.4]). Notably, one patient (ID 4) maintained a high EASI of 26.4 at one year but showed complete clearance of S. aureus, indicating that microbial reductions may occur independently of full clinical remission.
These results expand on previous findings that showed a 7.5-fold reduction in S. aureus within three days of treatment and nearly 100-fold by 28 days. This study provides the first real-world evidence that such reductions persist through one year of therapy.
High S. aureus colonization in AD is associated with increased inflammation and infection risk. The sustained microbial reduction observed in this study highlights an important secondary benefit of dupilumab that may contribute to improved skin barrier function and fewer flares.
“Future studies will focus on whether this reduction is maintained with longer durations of dupilumab treatment. We will also address whether this reduction is sustained when dupilumab is discontinued and how abundance reflects changes in AD severity off treatment,” researchers concluded.
Patients were part of the IRB-approved study “Longitudinal ‘Real-World’ Changes in Skin Microbial Ecology in AD Subjects” (NCT04170244). Microbial quantification was performed using CHROMagar™ Staphylococcus plates, and clinical assessments were aligned with routine dermatologic care.
