Nipple swab culture profile as a potential predictor of postoperative complications in autologous breast reconstruction: a retrospective study
Article information
Abstract
Background
The nipple is a potential source of pathogens because its lactiferous ducts act as direct conduits from the nipple–areolar complex to the breast parenchyma. Our previous studies identified breast microbiota as a factor in postoperative complications following immediate breast reconstruction using silicone implants and acellular dermal matrix. This study aimed to investigate the correlation between preoperative nipple swab microbiota and the incidence of surgical site infections (SSIs) after autologous breast reconstruction.
Methods
We conducted a retrospective chart review of patients who underwent autologous breast reconstruction following total mastectomy. Preoperative nipple swab cultures were obtained. Patient demographics, surgical characteristics, and complication rates were compared between culture-positive and culture-negative groups. Microbiological data, including antibiotic‑resistance profiles, were collected.
Results
Among 39 reconstructed breasts, 18 (46.9%) had positive preoperative nipple cultures. The mean duration of drain placement was significantly longer in the culture‑positive group (14.39±3.96 days) than in the culture‑negative group (12.14±2.76 days, P=0.045). Methicillin‑susceptible Staphylococcus epidermidis accounted for 55.0% of isolates. Of the four SSIs observed, three occurred in patients with positive preoperative cultures.
Conclusions
Although pathogen strains differed between preoperative and postoperative settings, obtaining preoperative nipple microflora cultures and determining antibiotic‑resistance profiles can guide immediate antibiotic selection for SSIs and enhance postoperative management.
INTRODUCTION
In recent years, autologous tissue transfer has become a cornerstone of breast reconstruction surgery. Both surgeons and patients favor autologous reconstruction for its natural appearance, tactile feel, and protective benefits against radiation therapy. However, autologous techniques carry higher postoperative complication rates than implant‑based methods [1], owing to longer operation times and surgical intervention at both donor and recipient sites. In particular, surgical site infections (SSIs) can delay healing and compromise both aesthetic and functional outcomes, which are crucial to patients’ psychological recovery from breast cancer. Understanding factors that influence SSI risk is therefore essential to optimize surgical techniques, postoperative care, and patient outcomes.
One potential pathogen source is the nipple, which communicates with the breast parenchyma via the lactiferous duct [2]. During mastectomy, incisions into the breast parenchyma may expose the ductal system to bacteria colonizing the nipple area. Immediate mastectomy in reconstruction is associated with an increased SSI risk [3]. Although preoperative skin disinfection is standard practice, the role of nipple microbiota in postoperative complications remains underexplored. Intraoperative use of nipple shields—sterile transparent films—has been introduced to reduce subclinical infection, but these offer only temporary, partial blockage and do not fully prevent trans‑areolar transmission [4-6].
Building on our department’s recent research linking breast microbiota to complications after implant‑based reconstruction with acellular dermal matrix [7], we investigated whether preoperative nipple swab microbiota correlate with SSIs following autologous breast reconstruction. By clarifying the nipple microbiota’s role, we aim to inform targeted perioperative strategies that improve patient safety and reconstructive outcomes.
METHODS
Patients
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).
Preoperative, intraoperative, and postoperative settings
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.
Assessment
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.
Statistical analysis
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.
RESULTS
Patient demographics and baseline characteristics
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.
Patient demographics and surgical characteristics
Preoperative microbiologic profile of the nipple
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.
Preoperative microbiologic profile of the nipple
Frequency of culture-proven preoperative nipple flora. MSSE, methicillin-susceptible Staphylococcus epidermidis; MRSE, methicillin-resistant Staphylococcus epidermidis.
Postoperative outcome
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.
Comparison of complication rates between preoperative microbiological colonization and non-colonization patients
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.
Characteristics of individual patients in four postoperative infection cases
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.
Representative clinical image of a patient who underwent postoperative infection following bilateral deep inferior epigastric perforator flaps. Corynebacterium striatum on the right nipple, Staphylococcus epidermidis and Corynebacterium tuberculosis on the left nipple were each collected in preoperative nipple cultures. (A) Preoperative, (B) intraoperative, and (C) postoperative photographs.
DISCUSSION
Bacteria present in the nipple flora can serve as a source of infection during operations requiring strict sterility—such as autologous flap reconstructions—because incisions extend into breast tissue. The multiple lactiferous ducts opening at the nipple form direct conduits into glandular tissue within the parenchyma, where bacteria concentrate in the peri‑areolar region. For this reason, the breast is classified as a clean‑contaminated surgical site [2].
Thornton et al. [10] showed that the breast’s microbiologic flora extend beyond the superficial layers into deeper tissues, indicating a risk of contamination when deep planes are exposed during mastectomy. Consistently, implant‑based reconstruction studies at our center have linked positive nipple cultures to a higher incidence of capsular contracture. Taken together, these findings may inform selection of perioperative antibiotic prophylaxis intended to reduce postoperative infections [7].
In our cohort, the duration of Hemovac drainage during hospitalization was significantly shorter in the culture‑negative group. Independent studies underscore that surgical drains can become conduits for microbial entry, highlighting the importance of strict infection‑control measures. Barbadoro et al. in their 2016 study [11] evaluated 872 abdominal operations in which drains were placed in 37% of cases; the overall SSI rate was 6.4%, but rose to 13.6% in patients with drains versus 2.4% in those without (P < 0.001). Felippe et al. in their 2007 [12] investigated women discharged with drains after breast cancer surgery and found that retained drains markedly increased SSI risk, with causative organisms matching those isolated from drainage fluid. These data illuminate infection‑control challenges and potential preventive strategies for breast‑surgery patients.
Our results suggest that preoperative nipple‑culture findings can expedite consensus on antibiotic choice by revealing likely SSI pathogens earlier than drainage‑fluid cultures. Although the sample was limited, 3 of 4 postoperative infections or hematomas exhibited organisms isolated on preoperative nipple culture, implying a possible association. Moreover, our data hint that shorter drainage duration may be linked to negative preoperative cultures, potentially lowering SSI risk.
Routine preoperative nipple cultures confer advantages once postoperative SSI develops. Clinicians can initiate targeted antibiotics immediately based on resistance profiles, rather than relying on empirical therapy while awaiting postoperative‐site culture results. At our institution, Hemovac‑tip and drain‑fluid cultures are also taken at removal, even in the absence of overt infection, to improve detection and management of infections that might otherwise present later.
However, this approach faces certain challenges. First, microorganisms isolated from nipple cultures do not always match SSI pathogens, implying that nipple flora may not directly cause infection. Second, postoperative SSI sources can vary, arising from donor sites or iatrogenic contamination, which weakens the correlation between preoperative nipple swabs and complications.
This study has several limitations. Nipple‑culture analysis in autologous‑flap patients may be influenced by incision location. Intraoperatively, nipple shields cannot be used over periareolar incisions—predominant in the nipple‑sparing mastectomies examined—thereby limiting superficial coverage. Furthermore, the retrospective design precluded assessment of important variables, such as tissue ischemia, that might influence infection risk. The sample size was relatively small, preventing statistically robust multivariate analyses of risk factors. Hence, while our findings support proactive management of subclinical infections, larger prospective studies are required to validate these observations.
In conclusion, among four postoperative infections in our series, three yielded positive preoperative nipple swab cultures, suggesting a correlation between nipple microflora and subsequent SSI. Although the specific pathogens differed pre‑ and postoperatively, obtaining preoperative cultures with resistance profiles enables prompt, tailored antibiotic selection and may improve postoperative outcomes. Further research is warranted to clarify the relationship between preoperative nipple microflora and postoperative infection risk.
Notes
No potential conflict of interest relevant to this article was reported.
Ethical approval
The study was approved by the Institutional Review Board of Korea University Anam Hospital (IRB No. K2025-0002-001) and performed in accordance with the principles of the Declaration of Helsinki. Written informed consent was waived by the IRB.
Patient consent
The patient provided written informed consent for the publication and use of her images.