Background

The incidence of mastitis has increased, and this disease can lead to long antibiotic courses and complications. Here, we aimed to identify the factors associated with antibiotic duration and recurrence of complicated mastitis.

Materials and methods

This retrospective cohort study was conducted in a tertiary hospital in Taiwan. All hospitalized patients diagnosed with mastitis (ICD-9 code 611.0) from Jan. 1, 2012, to Dec. 31, 2016, were enrolled. Patient characteristics and clinical data were obtained from the medical charts. Recurrence was defined as mastitis within the first year after the discontinuation of antibiotics for at least 7 days.

Results

In total, 214 females with a median age of 37 years old (IQR 33–45) were enrolled. A total of 148 patients (69.2%) underwent debridement, and 122 (57.0%) underwent biopsy. Histopathological examinations revealed granulation tissue in 44.6% (62/139) of the patients. Positive cultures were obtained in 65.9% (141/214) of the patients. Coagulase-negative staphylococci (64/141, 45.4%) was the most common pathogen, followed by Corynebacterium species (42/141, 29.8%). The median hospitalization length and antibiotic course were 7 (IQR 4–13) and 37 days (IQR 22–77), respectively. Three patients died of breast cancer during treatment. The recurrence rate was 18.5% (39/211). Younger age, corynebacterial infection, and pregnancy were associated with longer treatment durations (P < 0.001, 0.003, <0.001). Corynebacterial infection was associated with a 2.16-fold (95% CI: 1.11–4.20) increase in recurrence after adjusting for age.

Conclusion

Corynebacterial infection is associated with longer treatment courses and an increased recurrence rate of complicated mastitis. Therefore, specific treatments should be considered.