Streptococcus pyogenes Infection-Induced Primary Peritonitis in a Healthy Adult Female: A Very Rare Causative Agent

A 44-year-old woman with an unremarkable medical history presented to another hospital complaining of lower abdominal pain and nausea. The clinical presentation was consistent with an acute abdomen, raising suspicion of gastrointestinal tract perforation. However, imaging studies failed to provide evidence of perforation. Subsequently, the patient was diagnosed with peritonitis of unknown origin and promptly administered broad-spectrum antibiotics in a fasting state. Although the patient initially exhibited unstable symptoms, hemodynamics, and serology, she gradually improved over three days, with values approaching normal levels. On the sixth day of hospitalization, a follow-up abdominal computed tomography scan revealed pleural effusions, extensive ascites, and intra-abdominal stranding. The thickened wall of the small intestine and intra-abdominal stranding that were suggestive of peritonitis were further exacerbated. On the seventh day of hospitalization, aerobic and anaerobic blood cultures revealed the presence of Gram-positive cocci, later confirmed to be Streptococcus pyogenes, leading to the diagnosis of S. pyogenes infection-induced primary peritonitis. The source of infection was identified as a 10 mm hydrosalpinx in the left fallopian tube, suggesting the possibility of retrograde infection. The patient ultimately made a complete recovery without relapse and has been doing well since. This case report highlights a unique and rare occurrence of primary peritonitis caused by group A Streptococcus associated with infection from a hydrosalpinx in an otherwise healthy and young female patient. The diagnosis of primary spontaneous bacterial peritonitis in such an individual presents an uncommon clinical manifestation, emphasizing the importance of considering atypical sources of peritoneal infection in clinical practice.