Decolonization Strategies To Control Aerobic Gram-Negative Bacillary Infections in Breast Implant Surgery

To the Editor:

We read with interest the italian study on breast implant infections by Franchelli et al [1]. We congratulate them on an impressive clinical review of 240 patients during the course of two years. Their main finding, that aerobic gram-negative bacilli (AGNB) often cause surgical site infections (SSIs) following prosthetic breast implants, is important. However, they were unable to identify the source of these “abnormal” AGNB. This is not surprising as the study was limited to diagnostic cultures of the surgical site to confirm SSIs. Surgical site infections are generally endogenous in origin, that is, caused by potential pathogens carried by the patient at the time of surgery [2]. Only surveillance cultures of the throat and rectum can identify AGNB carriage.

Gut carriage of “abnormal” AGNB may occur in cancer patients in overgrowth concentrations. Cytotoxic chemotherapy and radiotherapy may damage the oral and gastrointestinal mucosa, increasing its permeability [3–5]. Additionally, the severity of the underlying disease may promote a shift from “normal” (e.g., Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Escherichia coli, methicillin-sensitive Staphylococcus aureus) to “abnormal” (Klebsiella, Proteus, Morganella, Enterobacter, Citrobacter, Serratia, Acinetobacter, and Pseudomonas species and methicillin-resistant S. aureus [MRSA]) flora in overgrowth concentration [5]. Those events predispose to translocation of normal and abnormal microorganisms, as well as enterococci, coagulase-negative staphylococci, and yeasts into the blood stream, followed by infection of the surgical site [5]. Remarkably, a recent meta-analysis, albeit of few studies, demonstrated that pre-operative chemoradiation was a risk factor for SSIs after breast surgery (odds ratio, 2.97; 95% confidence interval 2.43–3.63) [6]. The reason may be increased fibrosis, reduced vascularity, and hypoxia of the affected tissues accompanied with apoptosis, necrosis, and ulceration.

Decolonization policies have been proposed with the aim to prevent infections from endogeneous sources. The evidence supports decolonization with chlorhexidine or mupirocin to decrease MRSA SSIs in cardiothoracic and orthopedic surgery [7–9]. We have discussed previously the decolonization approach to control S. aureus infections in breast implant surgery [10].

The enteral combination of polymyxin and tobramycin is used commonly in decolonization tactics for the eradication of oropharyngeal and intestinal AGNB in overgrowth concentrations [11]. This combination was chosen because it covers most “abnormal” AGNB, including Pseudomonas species, and it is an in vitro synergistic combination. One-half gram of a paste or gel containing 2% polymyxin/tobramycin is applied onto the oropharyngeal mucosa four times a day to decolonize the oropharynx. Ten mL of a solution containing 100 mg polymyxin and 80 mg tobramycin are administered orally (or via the nasogastric tube) four times a day to decolonize the gut and to eradicate intestinal overgrowth of AGNB. Surgical patients who were decolonized successfully from AGNB had fewer infections, compared with controls in elective gastric surgery, colon surgery, and liver transplantation, albeit not of the breast [2,12]. If surveillance samples give positive results for AGNB, decolonization of the digestive tract, including the oropharynx, should be started pre-operatively [13].

We would argue that women with breast cancer requiring implant surgery would benefit from an extended pre-operative surveillance, including surveillance samples of the throat and rectum, and, peri-operative enteral antimicrobials, rather than a solely post-operative surveillance to detect infection followed by parenteral antimicrobials.