Infections Due to Corynebacterium kroppenstedtii With Focus on Granulomatous Lobular Mastitis for Tissue Specificity, Pathogenesis, Bacteriologic Workup, and Treatment.

Objective.—: To report the isolation and significance of C kroppenstedtii, features of patients with GLM, pathologic findings and mechanism, bacteriologic workup, and optimal treatment.

Design.—: Analysis of the cases with C kroppenstedtii at The University of Texas MD Anderson Cancer Center from 2016 to March 2024 for mechanistic insights.

Results.—: During a period of 8 years, isolates of C kroppenstedtii were obtained from 10 women and 7 men. All of the women, with an average age of 34 years (range, 18-61 years), presented with chronic or subacute mastitis, and were subsequently diagnosed with GLM. The men, with an average age of 66 years, had neoplastic diagnoses with the bacterium being commensal in 6 cases. Thus, C kroppenstedtii shows a predilection to infect the female breast (P < .001). Predisposing risks for GLM included childbirth in 8 women and nipple inversion in 2 women. Histopathology revealed xanthogranulomatous inflammation and Gram-positive bacilli within fat droplets or extracellularly. From GLM aspirates or tissue, the liquid culture media and/or anaerobic incubation yielded 9 of 10 isolates. Up to 14 tested strains were susceptible to vancomycin, linezolid, rifampin, and gentamicin. Nine women received extensive antimicrobial therapy.