Abstract
Granulomatous lobular mastitis (GLM) is a rare benign breast inflammatory disease that affects women of childbearing age. Corynebacterium species, especially Corynebacterium kroppenstedtii, was reported as the pathogen of GLM. A recent study showed that the C. kroppenstedtii complex is composed of C. kroppenstedtii and two novel species, C. parakroppenstedtii and C. pseudokroppenstedtii. The study presents seven C. kroppenstedtii-like strains isolated from GLM patients. However, they turned out to be six strains of C. parakroppenstedtii and one strain of C. pseudokroppenstedtii according to 16sRNA sequencing. In order to conduct a phylogenetic study, we further sequenced the fusA and rpoB genes, which were frequently employed in studies of Corynebacterium species. Novel Mass Spectral Peaks (MSPs) for C. parakroppenstedtii were created with Bruker MALDI-TOF MS. Then, the identification power of the MSPs was tested by C. parakroppenstedtii strains and remotely related Corynebacterum spp. The antibiotic sensitivity tests were performed according to the CLSI M45 guidelines. All of the strains were not resistant to β-lactams, vancomycin or linezolid. However, applying erythromycin and clindamycin could be fruitless. Phenotypic identification using a Vitek2 ANC ID card proved all of the C. parakroppenstedtii strains were identified as Actinomycete naeslundii. The test of Ala-Phe-Pro arylamidase and urease could be employed as the characteristics to distinguish C. pseudokroppenstedtii from C. parakroppenstedtii. Here, we present the identification, antibiotic sensitivity tests (ASTs) and epidemiological investigation of two novel C. kroppenstedtii-like species with the purpose of improving the understanding of C. kroppenstedtii-like species and related diseases.