Microbiology of periprosthetic infections following implant-based breast reconstruction surgery

Authors: Lisa AVE, Zeneli F, Mazzucco M, Barbieri B, Rietjens M, Lissidini G, Vinci V, Bartoletti M, Belati A, Bavaro D 

Affiliation: European Institute of Oncology and Humanitas University/IRCCS Humanitas Research Hospital, Milan 

Journal: Frontiers in Surgery, October 2024 

PMID: 39469540 

Key takeaways 

• Gram-positive organisms dominated implant infections after breast reconstruction, especially Staphylococcus species and Staphylococcus aureus. 

• Gram-negative infections were less common but clinically important, with Pseudomonas being the leading Gram-negative pathogen. 

• Overweight and obese patients had proportionally more Gram-negative infections than normal-BMI patients. 

• Positive preoperative MSSA/MRSA screening strongly predicted later Staphylococcus aureus infection. 

• Culture-driven therapy: preoperative cultures were often concordant with intraoperative cultures and should inform early antibiotic selection. 

Background 

Infection after implant-based breast reconstruction can lead to hospitalization, treatment delays, implant loss, and reconstructive failure. Empiric antibiotic selection is often broad and institution-dependent because there are no universally accepted guidelines for infected breast prostheses. 

This study examines the microbiology of severe periprosthetic infections requiring explantation, with the goal of making empiric therapy and prevention strategies more rational. 

Objective 

To characterize the organisms responsible for periprosthetic infections after implant-based breast reconstruction, compare Gram-positive and Gram-negative infection patterns, and identify patient or surgical factors associated with specific pathogen groups. 

Methods 

• Design: Multicenter retrospective cohort study at two major Italian breast centers, January 2018–March 2024; Level III. 

• Population: 214 patients with clinically infected implant-based breast reconstruction requiring implant removal; 9,800 total reconstructions were performed during the study period, with 2% requiring explantation. 

• Inclusion: History of mastectomy and implant-based reconstruction with clinical infection leading to surgical implant removal. 

• Cultures: Preoperative periprosthetic fluid/tissue cultures and intraoperative implant/tissue cultures at explantation were reviewed when available. 

• Variables: Age, BMI, smoking, diabetes, chemotherapy, radiotherapy, mastectomy type, axillary dissection, reconstruction type, drain duration, timing of explantation, MSSA/MRSA screening, antibiotic treatment, and culture results. 

• Pathogen groups: Gram-positive, Gram-negative, mixed, fungal, and mycobacterial infections; multidrug resistance defined as resistance to ≥3 antibiotics. 

• Statistics: Descriptive analysis with Chi-square/Fisher exact testing; significance set at P < 0.05. 

Results 

• Cohort: Mean age 53.9 years; mean BMI 25.0; 31.8% received radiotherapy, 41.1% chemotherapy, and 21.5% were active smokers. 

• Reconstruction: Immediate expander placement was most common (64.5%), followed by direct-to-implant reconstruction (20.1%) and expander-to-implant exchange (13.6%). 

• Culture availability: Preoperative cultures were available in 120 patients; intraoperative cultures were available in 151 patients. 

• Dominant organisms: Gram-positive bacteria were most common preoperatively (45.8%) and intraoperatively (53.7%). Staphylococcus species predominated, especially Staphylococcus aureus. 

• Staphylococcus aureus: Isolated in 34.1% of preoperative cultures and 32.7% of intraoperative cultures. 

• Gram-negative organisms: Less frequent but meaningful: 11.2% preoperatively and 17.3% intraoperatively. Pseudomonas was the most common Gram-negative organism. 

• Patient factors: BMI correlated with pathogen class (P = 0.007). Normal-BMI patients had more Gram-positive infections, while overweight and obese patients had higher proportions of Gram-negative infections. 

• Smoking: Smoking status correlated with pathogen distribution (P = 0.032); current and former smokers had more mixed infections. 

• Reconstruction type: Two-stage reconstruction had more mixed infections than direct-to-implant reconstruction (P = 0.019). 

• Culture concordance: Among patients with both positive preoperative and intraoperative cultures, results were concordant in 77.8% and partially concordant in 13.9%. 

• Timing: Most infections were early, occurring within 6 weeks (62.2%); pathogen distribution did not significantly differ between early and late infections. 

• Clinical presentation: Gram-negative infections were more likely to present with localized symptoms only rather than systemic symptoms (P = 0.040). 

• MSSA/MRSA screening: Positive preoperative MSSA/MRSA swabs were strongly associated with later Staphylococcus aureus infection (60.0% vs 23.4% with negative swab; P < 0.001). 

• Antibiotics: Fluoroquinolone-targeted therapy was associated with reduced intraoperative culture positivity (P = 0.008), although treatment selection was nonrandomized. 

Conclusion 

Severe periprosthetic infections after implant-based breast reconstruction requiring explantation are most often caused by Gram-positive organisms, particularly Staphylococcus aureus. However, Gram-negative organisms, especially Pseudomonas, remain important and should be considered when selecting empiric antibiotics, particularly in higher-BMI patients or patients with localized presentations. 

Strengths

• Multicenter cohort from two high-volume breast cancer centers. 

• Includes both preoperative and intraoperative cultures, allowing assessment of culture concordance. 

• Links pathogen class to clinically useful variables, including BMI, smoking, reconstruction type, symptoms, and MSSA/MRSA screening. 

Limitations 

• Retrospective design with incomplete culture data and dependence on medical record accuracy. 

• No data on surgical measures used for prevention of infection during implant placement, such as disinfection or antibiotic irrigation, which may have differed between the surgeons and centers. 

• No data on drain placement and drain care/dressings. 

• No data on routine antibiotic prophylaxis after implant placement. 

• Only includes infections severe enough to require explantation, so findings may not apply to milder infections managed with antibiotics or salvage. 

• Antibiotic selection was not standardized or randomized, limiting conclusions about treatment effectiveness. 

• No detailed implant salvage outcomes, reconstructive abandonment rates, or long-term recurrence data. 

• Institutional microbiology and resistance patterns may not generalize to other regions or hospitals. 

Clinical relevance 

Empiric therapy should include reliable Gram-positive coverage, with MRSA coverage guided by local risk and patient history. Add Gram-negative coverage, especially antipseudomonal coverage, when the patient is overweight/obese, has drainage or a fluid collection, has prior antibiotic exposure, or when local antibiograms support it.  Preoperative MSSA/MRSA screening could be helpful: a positive result should trigger decolonization and should raise suspicion for Staphylococcus aureus if postoperative infection develops.