Mixed local infection with Escherichia coli and Eggerthella lenta bloodstream infection following surgery for acute appendicitis: A case report

This case describes a rare post-appendectomy abdominal wall infection caused by a dual pathogen of Eggerthella lenta (a rarely reported anaerobic commensal bacterium) and extended-spectrum β-lactamase (ESBL)-producing Escherichia coli, complicated by subcutaneous emphysema and intraperitoneal free air. It adds to the literature by documenting the clinical presentation, diagnostic approach, and successful management of this uncommon co-infection, which is rarely reported in existing studies. Symptoms and clinical findings : A 68-year-old male presented with poor incision healing, local erythema, pain, purulent discharge, and persistent fever (peak 38.7°C) after open appendectomy for perforated appendicitis. Empirical ceftriaxone treatment failed at an outside hospital. On admission, diffuse abdominal tenderness, guarding, and palpable crepitus (subcutaneous emphysema) in the mid-to-lower abdomen were observed. Laboratory tests showed leukocytosis (20.61 × 10⁹/L, 81.5% neutrophils), elevated procalcitonin (1.300 ng/mL), and hypoalbuminemia (22.7 g/L). CT confirmed surgical site exudate, abdominal wall subcutaneous emphysema, and minimal intraperitoneal free gas. Diagnoses : Postoperative abdominal wall infection, abdominal wall subcutaneous emphysema, intraperitoneal free air, co-infection with E. lenta and ESBL-producing E. coli, and hypoalbuminemia. Interventions : Incision and drainage with vacuum sealing drainage (VSD) on admission, followed by a second debridement with VSD on postoperative day 7. Antimicrobial therapy was initiated empirically with cefoperazone/sulbactam plus ornidazole, then adjusted to meropenem based on susceptibility results. Outcomes : Abdominal wall inflammation resolved, infection markers decreased significantly, and wound cultures became negative by day 10. The patient was discharged successfully with no complications during follow-up. Conclusion : This case underscores that for patients with refractory post-appendectomy infections, clinicians should consider the possibility of rare pathogen co-infections such as Eggerthella lenta and strengthen etiological testing by combining methods like MALDI-TOF MS and 16S rRNA sequencing to avoid missed diagnoses; it also highlights that carbapenems such as meropenem are effective therapeutic options when empirical antibiotics fail to treat infections involving ESBL-producing bacteria, and that the combined strategy of sequential debridement, vacuum sealing drainage, targeted antimicrobial therapy, and continuous monitoring of infection markers is critical to successfully managing complex postoperative abdominal infections.