Atopic dermatitis (AD) is a chronic, multifactorial inflammatory skin disease affecting 20–30% of children, characterized by epidermal barrier dysfunction and an exaggerated immune response. A primary complication in these patients is the frequent colonization or secondary infection by Staphylococcus aureus, which is present in approximately 70% of lesional skin compared to only 10% in healthy individuals. This pathogen exacerbates the disease by producing superantigens and forming biofilms, which protect the bacteria from host antimicrobial peptides, phagocytosis, and antibiotic treatments. Because distinguishing between disease flares and mild secondary infections is difficult, antibiotics are often used empirically; however, rising resistance rates to first-line therapies necessitate a deeper understanding of bacterial characteristics. This study was conducted to determine if biofilm production and specific antimicrobial susceptibility patterns are directly linked to clinical outcomes and disease severity in pediatric patients.
Methods
This longitudinal observational study analyzed 136 S. aureus isolates obtained from the nares and skin of 26 pediatric patients with moderate-to-severe AD over 18 months. Antimicrobial susceptibility was determined via the disk diffusion method, while biofilm production was quantified using a crystal violet microtiter assay. Researchers also performed PCR to detect resistance genes, including ermA, ermB, ermC, and msrA. Clinical severity was tracked using the SCORAD index, correlating bacterial traits with treatment response and the use of adjunctive dilute bleach baths.
Key Findings
• Prevalence of Biofilms: 60.2% of the S. aureus isolates were classified as moderate-to-strong biofilm producers.
• Correlation with Severity: High biofilm production was significantly associated with severe AD at baseline (p = 0.01) and persistent moderate-to-severe disease throughout the study (p = 0.01).
• Treatment Failure: Isolates from patients who failed to show clinical improvement were more likely to produce biofilms (p = 0.04).
• Antibiotic Resistance: Resistance rates exceeded the 15% threshold for several antibiotics, including penicillin (75.7%), gentamicin (36%), clindamycin (25%), and erythromycin (25%).
• Bleach Bath Impact: Patients using adjunctive dilute bleach baths (0.006%) harbored isolates with significantly higher resistance to ciprofloxacin (p < 0.0001).
• Genetic Markers: The iMLSB phenotype (inducible macrolide–lincosamide–streptogramin B resistance) was found in 14.7% of isolates, with the ermA gene detected in 80% of these cases.
The research highlights a critical link between S. aureus biofilm formation and clinical treatment failure in pediatric AD, suggesting that biofilms act as a protective reservoir that facilitates bacterial persistence and resistance. The novelty of this study lies in its longitudinal evidence that biofilm-producing strains are directly tied to the inability to achieve a significant reduction in disease severity (SCORAD). Future implications suggest that clinical management must shift toward culture-guided, targeted therapeutic strategies rather than empirical antibiotic use. Furthermore, there is an urgent need to develop non-antibiotic treatments that specifically target biofilm production and quorum sensing to restore the skin microbiome without further driving antimicrobial resistance.
Link to the study: https://www.mdpi.com/2076-2607/14/2/311
