Atypical Breast Abscess in Pregnancy: A Case of E. coli and E. faecalis Co-Infection

Introduction. Mastitis is a common type of breast tissue inflammation in women and is typically self-limited. In rare occurrences, it can progress to abscess formation involving Staphylococcus aureus, Streptococcus species, and anaerobes. This case presents an atypical progression of mastitis with abscess formation involving multidrug-resistant Escherichia coli and Enterococcus faecalis, highlighting a unique dermatologic presentation of a somewhat common soft tissue infection. Case Presentation. A 36-year-old woman at 36 weeks gestation presented with unilateral localized tenderness, erythema, and induration. Initially diagnosed with mastitis at 10 weeks gestation, she was treated with cephalexin after culture confirmed Staphylococcus aureus. However, her lesion evolved to purulent nipple discharge associated with intense tenderness and diffuse erythema of the breast. Repeat cultures identified Escherichia coli and Enterococcus faecalis, with resistance to several first-line agents, posing a therapeutic challenge. Discussion. Breast abscesses in pregnancy are rare, especially those involving gram-negative or enteric flora. The unusual resistance profile further complicates management. Though mastitis is commonly treated with antibiotics, abscesses often require drainage prior to complete resolution. This case highlights the importance of maintaining a broad differential in breast infections while utilizing culture-directed therapy in guiding treatment and preventing complications, particularly in pregnant patients where antibiotic options are limited. Conclusion. This case illustrates the challenges associated with diagnosing and managing atypical breast abscesses. A broad differential diagnosis, paired with early culture and sensitivity testing, is critical for initiating targeted therapy and optimizing patient outcomes.