The Distribution of Aerobic and Anaerobic Bacteria in the Etiology of Granulomatous Mastitis and Their Resistance to Antimicrobial Agents

Abstract

Objective: Granulomatous mastitis (GM) is a rare chronic inflammatory disease of the breast. The etiological role of bacteria in granulomatous mastitis, which is the most common type of non-lactational mastitis, is not exactly known. Methods: Our study was carried out with tissue and/or abscess cultures of 46 patients who applied to Istanbul University - Cerrahpasa, Cerrahpasa Medical Faculty Hospital, Department of General Surgery, Breast Outpatient Clinic, and Emergency Surgery Service, between January 2015-January 2016 and were diagnosed with GM according to the results of histopathological and clinical examinations. In addition to conventional methods, aerobic bacteria isolated from the samples were identified with the BD Phoenix (Becton, Dickinson Company, Maryland, USA) and anaerobic bacteria with the API 20A (bioMerieux, Marcy l'Etoile, France) kit, and bacterial identification was made by PCR amplification of 16S rRNA from samples in which bacteria were seen in Gram staining but not grow in culture. Antimi-crobial susceptibilities of the bacteria were determined by disc diffusion and gradient test methods. The results were evaluated according to EUCAST 2016 criteria. Results: When the culture results of the patients diagnosed with GM were evaluated, growth was observed in 20 (43.7%) patient materials, and it was not detected in 26 (56.5%) patient materials. Corynebacterium species were detected in 12 (26.1%) of 46 patients. C. kroppenstedtii was isolated in 7 (15.2%), C. urealyticum in 3 (6.5%), and C. amycolatum in 2(4.3%) patients. S. aureus grew in 2 (4.3%) patients, and Klebsiella spp. and Proteus spp. grew in 1 patient each. Peptostreptococcus spp. (3 samples, 6.5%) and B. fragilis (2 samples, 4.3%) were the anaerobic bacteria grown in cultures. Different bacterial species grew together in 6 (30%) of 20 GM patient samples. PCR amplification of 16S rRNA made from pus samples of 19 Gram stain positive but culture-negative cases resulted in C. kroppenstedtii (3 samples), S. epidermidis (3 samples), and anaerobic bacteria such as Peptostreptococcaceae bacterium, Cutibacterium spp., C. acnes, B. breve have been isolated in 1 sample each. Conclusions: We believe that determining aerobic and anaerobic agents that cause granulomatous mastitis and applying specific treatment for the etiological agents rather than using broad-spectrum antibiotics which could lead the antimicrobial resistance, will be beneficial. Antibiotics such as penicillin, gentamicin, vancomycin, and linezolid, which are effective on Gram-positive rods (Corynebacterium species), can be added to the treatment, especially in culture negative cases of granulomatous mastitis.