Peptoniphilus harei is a Gram-positive anaerobic coccus, first isolated from purulent material in the sacrum, gastric sinus, and peritoneal sites by Murdoch and colleagues [14]. Peptoniphilus harei can colonize the gastrointestinal tract, skin, oral cavity, vagina, and upper respiratory tract [4, 15, 16]. It is not a common single-pathogen, but it often co-infects with other microorganisms, and is considered an anaerobe coexisting in chronic wounds or diabetic ulcers [5]. Our literature review of reported cases infected by Peptoniphilus harei (Table 3) found instances involving implants, brain, abdomen, vessels, etc [4,5,6,7,8, 15,16,17,18]. Only three cases of breast abscess caused by Peptoniphilus harei have been reported, all with concurrent Actinomycosis infection [6,7,8]。 In contrast, the present case is the first to document Peptoniphilus harei as the sole pathogen responsible for a breast abscess. Furthermore, previously reported cases of breast infections involved primary breast abscesses in patients without a history of malignancy or prior oncologic treatments such as chemotherapy or radiotherapy. This distinguishes our case as a unique presentation of Peptoniphilus harei infection in a breast cancer patient following multimodal cancer therapy.
In the management of breast abscess, the crucial aspect is identifying the causative pathogen to facilitate recovery and prevent recurrence [1]. The diagnosis of the pathogen is primarily achieved through culture of purulent exudate. Studies suggest that postoperative surgical site infections in the breast area increase the risk of breast cancer recurrence [2]. This underscores the importance of early and effective antimicrobial treatment. Empirical antibiotic treatment is common in treating breast abscess, with adjustments based on bacterial epidemiology [1, 2]. However, choosing antibiotics based on identified pathogens is preferable.
Identification of Peptoniphilus harei can be done through phenotypic tests, Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS), and molecular typing [4, 5, 16]. As of now, there is no established antibiotic treatment protocol for Peptoniphilus harei infection. According to the 2016 CLSI guidelines, Peptoniphilus harei is sensitive to a range of antibiotics, including penicillin, amoxicillin-clavulanic acid, piperacillin-tazobactam, clindamycin, meropenem, imipenem, linezolid, vancomycin, moxifloxacin, and metronidazole [15]. Additionally, Peptoniphilus harei is sensitive to ampicillin, ceftriaxone, chloramphenicol, cefotaxime, and cefoxitin [5, 15, 18]. However, some experimental data indicate that certain strains have shown resistance to penicillin, clindamycin, chloramphenicol, tetracycline, erythromycin, and quinolones [15, 19, 20]. Thus, further clinical data is needed to establish a clear treatment approach for Peptoniphilus harei infection. In our case, we used penicillin and metronidazole initially following pathogen identification. And after 7 days, the regimen was switched to cefazolin to prevent nosocomial infections. The patient showed significant control of the infection under this antibiotic regimen, suggesting the effectiveness of penicillin and metronidazole against Peptoniphilus harei.
Endoscopic assisted breast surgery (EABS), conducted through incisions in the axilla or periareolar region, has become widely used in breast cancer surgery. Its major advantages include discreet incisions and minimal scarring, resulting in better aesthetic outcomes and increased patient satisfaction [9,10,11,12]. Furthermore, endoscopic surgery provides a broader surgical field and a better differentiation of anatomical structures [9, 11]. In breast cancer surgery, endoscopic surgery shows comparable oncological safety to open surgery [9,10,11,12,13]. For breast-conserving surgery (BCS), endoscopic assisted breast conservation surgery (E-BCS) offers advantages over conventional breast conservation surgery (C-BCS), including smaller scars and improved cosmetic results, without compromising oncologic outcomes [21,22,23,24]. The potential complications of EABS include infection, skin burns, subcutaneous emphysema, intraoperative or postoperative bleeding, and flap necrosis [9, 11, 13, 25]. However, these complications occur at a low frequency and are similar to those associated with open surgery [9, 11, 13]. Although breast surgery is generally classified as a clean procedure, the reported incidence of acute postoperative infections ranges around 4% [26]. For BCS, early surgical site infection (SSI) rates have been reported between 1.3% and 3.1% [27, 28]. The most common causative pathogens of postoperative SSIs are Gram-positive bacteria, particularly Staphylococcus aureus [26, 27]. Risk factors for SSIs following breast surgery include surgical technique and duration, neoadjuvant chemotherapy or radiotherapy, and patient-related factors such as smoking, alcohol consumption, obesity, hypertension, and diabetes [29, 30]. To date, there is a lack of literature review specifically addressing SSIs following EABS or E-BCS. We think the risk factors for SSIs following EABS are largely consistent with those of open surgery. A retrospective study reported that postoperative infections following E-BCS were frequently associated with the use of absorbable implant materials, with 7 out of 60 patients developing infections [9]. We believe that prolonged operative time, compromised vascularity of glandular skin flaps, and the use of absorbable implants may represent unique contributors to SSIs in E-BCS. In our case, the patient underwent E-BCS following neoadjuvant chemotherapy. The operative time was not prolonged (approximately 3 h), and the perioperative course was uneventful. Therefore, we do not consider the infection to be directly related to the endoscopic assisted surgical procedure.
Radiotherapy is an important treatment modality for breast cancer. However, it can also lead to serious side effects, including radiation dermatitis, cardiac toxicity, soft tissue fibrosis, fat necrosis, and lymphedema [31,32,33,34]. A retrospective study showed that 20% of tumor patients undergoing radiotherapy experienced unplanned hospitalizations within the 90 days of treatment, with 10% of cases related to infections [35]. Breast cancer patients who undergo autologous transplantation reconstruction after radiotherapy have a significantly increased risk of infection due to soft tissue fibrosis and impaired vascular function [31]. Another study revealed that 6% of breast cancer patients undergoing breast-conserving surgery developed delayed abscesses after radiotherapy, with a median time of 5 months post-surgery [36]. In our case, the patient developed a breast abscess 5 months after undergoing endoscopic breast-conserving surgery and 3.5 months after radiotherapy. We consider the possible reason to be the patient’s compromised local immune function due to fibrosis and tissue damage after radiation and chemotherapy. This may have facilitated a skin infection by Peptoniphilus harei, ultimately resulting in the formation and rupture of a breast abscess. Due to the unclear extent of infection and extensive radiation-induced scarring, aggressive debridement posed a significant risk of poor wound healing and undesirable breast deformity, making primary closure unfeasible. Therefore, a more conservative approach was adopted. Under local anesthesia, we performed limited debridement to minimize surgical trauma, aiming to remove necrotic tissue as thoroughly as possible, identify the causative pathogen, and control the infection. Given that complete debridement was not performed, the use of negative pressure wound therapy was contraindicated [37]. An open wound management strategy with daily dressing changes was employed instead. Once the wound showed clear signs of improvement, including the development of healthy granulation tissue, we proceeded with secondary closure. Although the tissue defect was substantial and could have been reconstructed using a lateral thoracic artery perforator flap [38], the patient declined this option. As a result, direct closure was performed. Despite noticeable changes in breast contour postoperatively, the patient reported a high level of satisfaction with the overall outcome.
Here, we report a rare case of a patient who developed a breast abscess caused solely by Peptoniphilus harei after undergoing endoscopic assisted breast cancer surgery and radiotherapy. Optimizing diagnostic methods to promptly identify the pathogen is crucial for ensuring the patient receives the best possible treatment Fig. 6.
Breast ultrasonography revealed skin thickening of the left breast and soft tissue swelling around the surgical incision. In the deep region of the incision (corresponding to the 1–2 o’clock position), a hypoechoic area measuring approximately 50 × 14 mm was identified, with poor sound transmission. Fluid movement was observed upon probe compression. These findings are suggestive of postoperative soft tissue swelling with abscess formation in the surgical area of the left breast.
