Clinical metagenomic analysis of bacterial communities in breast abscesses of granulomatous mastitis

Background: Granulomatous mastitis (GM) is a chronic inflammatory breast lesion. Its etiology remains incompletely defined. Although mounting evidence suggests the involvement of Corynebacterium in GM, there has been no systematic study of GM bacteriology using-omics technology. Methods: The bacterial diversity and relative abundances in breast abscesses from 19 women with GM were investigated using 16S rDNA metagenomic sequencing and Sanger sequencing. A quantitative PCR (qPCR) assay was also developed to identify Corynebacterium kroppenstedtii. Results: A bioinformatic analysis revealed that Corynebacterium was present in the 19 GM patients, with abundances ranging from 1.1% to 58.9%. Of note, Corynebacterium was the most abundant taxon in seven patients (more than a third of the subjects). The predominance of Corynebacterium kroppenstedtii infection (11 of 19 patients, 57.9%) was confirmed with Sanger sequencing and the qPCR assay. Conclusions: This study profiled the microbiota of patients with GM and indicated an important role for Corynebacterium, and in particular C. kroppenstedtii, in the pathogenesis of this disease. (C) 2016 The Authors. Published by Elsevier Ltd on behalf of International Society for Infectious Diseases.