We initially identified 46 patients who underwent autologous flap breast reconstruction from October 2020 to May 2022. The exclusion criteria were: (1) autologous flaps for primarily aesthetic indications (e.g., latissimus dorsi [LD] flap for Poland’s syndrome in male patients); (2) loss to follow‑up exceeding 6 months; and (3) missing data. Following these exclusions, a retrospective analysis was conducted of 36 patients (39 breasts). Three patients underwent bilateral reconstructions, yielding separate data for each breast. Reconstruction methods—LD flap, deep inferior epigastric perforator (DIEP) flap, and transverse rectus abdominis myocutaneous (TRAM) flap—were performed by two specialized plastic surgeons, with flap selection individualized based on breast design and the clinical judgment of the operating surgeons. This retrospective analysis was approved by the Institutional Review Board of Korea University Anam Hospital (protocol number K2025-0002-001).

Sterile swab cultures were collected from each nipple with a cotton‑tipped applicator the day before surgery for Gram stain and culture. Separate applicators were applied with slight pressure to the tip of the dry nipple, in order to limit sampling to the nipple surface without capturing areolar skin flora. Patients were instructed to shower with antiseptic chlorhexidine soap a day before surgery [7]. Prophylactic cephalosporin was administered intravenously 1 hour before surgery. Intraoperatively, povidone–iodine was routinely applied to ensure field sterility. Sterile Loban transparent film (3M Healthcare) served as a nipple shield on both nipples; shields were omitted in patients with peri‑areolar incisions. After mastectomy, shields covered incisions during the transition to reconstruction. The breast pocket was irrigated with Betadine and triple antibiotic solution (Adam’s solution [8]) before flap inset. Postoperatively, two Hemovac drains were placed at donor and recipient sites for fluid collection and were removed once daily output fell below 30 mL on two consecutive days. Drain fluid and tip cultures were obtained at removal.

Preoperative data included height, weight, body mass index (BMI), hypertension, diabetes mellitus, smoking status, and manual evaluation of breast volume and design preoperatively. Neoadjuvant and adjuvant chemotherapy and radiotherapy histories were collected retrospectively after surgery. Patients were monitored for complications via clinical exams, dressing changes, and laboratory tests—complete blood count, erythrocyte sedimentation rate, and C‑reactive protein (CRP). SSIs were identified using Centers for Disease Control and Prevention criteria [9]. In SSI cases, drain fluid and superficial swab cultures were obtained, and empirical antibiotics were administered guided by preoperative nipple culture results. Immediate hematomas were diagnosed clinically by bruising, swelling, and bloody Hemovac drainage. Donor‑site complications (e.g., tissue and fat necrosis) were confirmed and managed with surgical debridement as needed. Seromas were identified at outpatient follow‑up when fluid collections persisted after three or more aspirations.

All statistical analyses were conducted using SPSS Statistics (version 24.0, IBM Corp.). A P-value <0.05 was considered statistically significant. For categorical variables, the chi-square test and Fisher exact test were employed to analyze statistical significance.

A total of 36 patients undergoing autologous reconstruction were enrolled, with a mean age of 52.6 years and mean BMI of 25.1 kg/m². Mean preoperative breast volume was 341.3 mL. Eighteen breasts had positive nipple cultures and 21 were culture‑negative; groups did not differ significantly in age, BMI, or laterality (Table 1). Reconstruction types included seven LD flaps, 27 DIEP flaps, and five TRAM flaps, with no significant difference between culture‑positive and ‑negative groups (P=0.799). The mean duration of drain placement was longer in culture‑positive breasts (14.39 ± 3.96 days) than in culture‑negative breasts (12.14 ±2.76 days, P =0.045). No significant differences were observed in preoperative and postoperative chemotherapy or radiotherapy history.

Analysis of preoperative nipple cultures (Table 2) identified 20 microorganism species among 18 positive samples, with some samples yielding multiple species. Fig. 1 shows the distribution of isolates: 95% were Gram-positive, and only one Gram-negative species was detected. Methicillin-susceptible Staphylococcus epidermidis was most frequent (55%), followed by Corynebacterium striatum (10%); all other species were present at 5% each.

In 14 observed cases, which included overlapping instances among patients, we noted four cases of postoperative infection, four cases of hematoma, no cases of seroma, and six cases of fat necrosis. Table 3 compares the complication rates between patients with and without preoperative microbiological colonization. Out of 39 breast operations, 18 had a positive preoperative nipple swab culture. Three of the four postoperative infections occurred in patients with a positive preoperative culture. A similar pattern was noted with postoperative hematoma. Of the six fat necrosis cases, two occurred in culture‑positive and four in culture‑negative breasts.

Table 4 details four postoperative infection cases involving three patients (one bilateral). In Case 1, a 40-year-old underwent bilateral nipple‑sparing mastectomy with DIEP flap reconstruction. Preoperative nipple cultures grew Corynebacterium spp. and Staphylococcus epidermidis. On postoperative day (POD) 11, Pseudomonas aeruginosa was isolated from Hemovac fluid; the patient had a peak fever of 38.5 °C on POD 1 and a CRP of 125.13 mg/L on POD 3. Empirical intravenous antibiotics began on POD 2, followed by surgical debridement and targeted therapy, resulting in improvement.

Case 2 involved a 55-year-old woman who underwent skin‑sparing mastectomy with immediate DIEP reconstruction. Despite negative preoperative cultures, she developed an infection marked by purulent green discharge and elevated CRP and absolute neutrophil count. No pathogen was isolated, but P. aeruginosa was clinically suspected. The patient responded favorably to intravenous antibiotics and surgical debridement, achieving complete recovery.

The final case involved a 66-year-old patient who underwent skin‑sparing mastectomy with immediate TRAM flap reconstruction. Preoperative cultures grew Corynebacterium spp. Postoperatively, persistent discharge and necrosis prompted tissue cultures, isolating Enterococcus faecalis on POD 9 and Acinetobacter baumannii on POD 11. Intravenous amikacin was initiated on POD 2 based on the preoperative cultures, and the antibiotic regimen was adjusted following confirmation of the pathogens based on recommendations from the infectious disease department.

Fig. 2 illustrates a culture‑confirmed SSI after bilateral DIEP reconstruction. Preoperative nipple cultures of the right and left nipples grew C. striatum and S. epidermidis plus Corynebacterium tuberculosis, respectively. Postoperatively, P. aeruginosa was isolated from donor‑site dehiscence cultures. The patient fully recovered after treatment with ceftazidime and surgical debridement.