Profiling Microbial Communities in Idiopathic Granulomatous Mastitis

Area of Science:

• Microbiology
• Inflammatory Diseases
• Breast Health

Background:

• Idiopathic granulomatous mastitis (IGM) is a rare, benign breast condition with an unclear cause.
• Lactational mastitis (LM) is a common infection in breastfeeding women, serving as a contrast for etiological investigation.

Purpose of the Study:

• To investigate the microbial etiology of IGM by comparing the bacterial flora in pus and skin samples from IGM and LM patients.
• To identify potential microbial differences and associations in IGM pathogenesis.

Main Methods:

• 16S rRNA gene sequencing was performed on DNA extracted from paired pus and skin swabs of 21 IGM and 3 LM patients.
• Metagenomic analysis was conducted using a customized R-resource, with statistical comparisons of microbial profiles.
• Multivariable association analyses were adjusted for antibiotic treatment and multiple comparisons.

Main Results:

• Significant ecological dissimilarity was observed across IGM pus, IGM skin, LM pus, and LM skin samples (PERMANOVA, p < 0.001).
• IGM pus samples exhibited higher microbial diversity than paired IGM skin samples (p = 0.022).
• Corynebacterium kroppenstedtii was more abundant in IGM pus than skin (p = 0.022), alongside other significant species and genera, but no dominant causative agent was identified.

Conclusions:

• Microbial profiles in IGM and LM are distinct.
• The high inter-patient variability and polymicrobial nature of IGM pus samples preclude identifying a specific bacterial genus or species as the sole infectious cause.