Abstract
BACKGROUND: Primary cicatricial alopecia (PCA) is a group of disorders causing irreversible hair loss because of hair follicle destruction. Although bacterial colonization is suspected to contribute to PCA pathogenesis, its role remains unclear. OBJECTIVE: To investigate bacterial colonization patterns and antibiotic susceptibility profiles in patients with PCA compared to those with non-inflammatory scalp conditions. METHODS: This retrospective study analyzed bacterial cultures from scalp swabs of 161 subjects (68 patients with PCA and 93 controls) at a tertiary hospital between June 2011 and December 2023. Bacterial species and antibiotic resistance rates were evaluated using subgroup analyses of neutrophilic PCA (NCA). RESULTS: PCA cultures showed a higher prevalence of Staphylococcus aureus (24.3%) and S. lugdunensis (8.1%) than controls, where S. capitis (54.5%) was predominant. Gram-negative bacteria were more frequent in the PCA group (13.5%) than in the control group (9.9%), with Klebsiella spp. (10.9%) being the most prevalent. Resistance rates were significantly higher in PCA for benzylpenicillin, fusidic acid, erythromycin, clindamycin, oxacillin, and telithromycin (p<0.05). Methicillin-resistant S. aureus was identified in 15% of S. aureus isolates from NCA cases. Gram-negative bacteria in PCA also exhibited increased resistance to ampicillin and ampicillin/sulbactam. CONCLUSION: PCA exhibits distinct bacterial colonization and elevated antibiotic resistance, particularly in the neutrophilic subtypes. Bacterial culture and susceptibility testing are essential for targeted therapies in clinical practice. Further multicenter microbiome analyses with mechanistic studies are needed to elucidate bacterial contributions to PCA pathogenesis.