Breast Abscess Caused by Serratia Marcescens One Year After Mastopexy

Mastopexy is a widely performed plastic surgery procedure for aesthetic breast correction and may present infectious complications. The main agents isolated in this context are staphylococci, especially Staphylococcus aureus. A 38-year-old female patient, previously healthy, with a history of breastfeeding both children up to six months of age, underwent mastopexy on 06/24/2023 with a 275 mL implant in the subglandular plane, combined with lipoabdominoplasty, without immediate surgical complications. Approximately one year after the procedure, she developed pain and discomfort in the left breast, which led to hospital admission. Empiric antibiotic therapy with amoxicillin-clavulanate was started and, after therapeutic failure, trimethoprim-sulfamethoxazole (TMP-SMX) was used with initial clinical improvement; however, there was subsequent recurrence and worsening of the inflammatory condition. She then underwent ultrasound-guided breast aspiration and secretion culture, with sample collection performed on 06/28/2024. Serratia marcescens was identified, and the antibiogram showed resistance to aztreonam, cefepime, ceftazidime, and ciprofloxacin, with susceptibility to amikacin, gentamicin, meropenem, imipenem, ertapenem, piperacillin-tazobactam, trimethoprim-sulfamethoxazole, and levofloxacin (with increased exposure). The strain produced extended-spectrum beta-lactamase (ESBL) and had possible expression of AmpC beta-lactamase, which limits the use of cephalosporins and penicillins even when in vitro susceptibility appears favorable. Despite susceptibility to TMP-SMX, the favorable initial clinical response followed by recurrence raised the hypothesis of bacterial biofilm formation. After multiple antibiotic cycles, successive recurrences, and hyperbaric oxygen therapy sessions, the patient underwent removal of the breast implant and surgical drainage of the abscess on 08/13/2024, with progressive clinical improvement associated with TMP-SMX use. Breast abscess caused by Serratia marcescens, an opportunistic, multidrug-resistant enterobacterium, is uncommon, especially in late infections, and represents a therapeutic challenge. This report reinforces the importance of detailed microbiological investigation in atypical cases and therapeutic adaptation based on susceptibility testing. It highlights the need for vigilance in late postoperative follow-up and strict infection-control protocols in elective procedures, contributing to clinical management and prevention of similar cases.