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WSU Medical School

Training Level

Medical Student


Wayne State University


Background: Actinomyces, a filamentous, gram-positive, facultative anaerobic bacterium, is part of the commensal flora of the oral cavity, gastrointestinal tract and the female genital tract. Actinomyces have low virulence potential and cause opportunistic infection associated with injury to the mucosal barrier, such as that occurring from surgery, trauma, peritoneal dialysis catheter, viscus perforation or intrauterine devices. Infections associated with actinomyces are often reported by imaging studies as masses, pseudotumors or abscesses. Fistulas and sinus tract formation are not uncommon. Primary peritonitis with actinomyces is very rare. We report a case of Actinomyces peritonitis in an elderly gentleman with a history of pancreatic cancer. Case Report: An 88 year-old man with history of adenocarcinoma of the pancreatic head diagnosed 15 months ago, malignant biliary stricture with common bile duct stent on palliative chemotherapy, presents to the emergency department with 1-2 weeks of worsening abdominal pain, anorexia and malaise. The patient was afebrile, tachycardic and hypotensive. Initial labs include elevated WBC, AKI, LFT and lactic acidosis. Abdominal imaging showed cirrhotic liver, cholecystitis and increasing ascites with peritoneal enhancement. Empiric Ceftriaxone and Metronidazole were initiated. A cholecystostomy tube was placed by interventional radiology. Bile fluid culture was positive for Klebsiella pneumoniae and streptococcus species. Paracentesis was performed and fluid analysis showed 43,000 WBC with > 95% neutrophils. The patient progressed to septic shock following the procedures and broad spectrum antibiotics with vancomycin and pipercillin-tazobactam were initiated. Five days later, ascetic fluid culture revealed Actinomyces israelii. The patient was started on Ampicillin-Sulbactam with plan for six months of antibiotic therapy. The patient was discharged in stable condition with scheduled follow up with infectious diseases. Conclusion: Peritonitis due to Actinomyces is very rare, and should remain in the differential diagnosis especially in cases of peritonitis not responding to typical empiric antibiotics therapy for primary peritonitis. Primary pelvic-abdominal peritonitis without abscess formation is very rare yet possible. The therapy of choice for actinomycosis is high-dose penicillin for 2-4 weeks, followed by 2-6 months of oral antibiotics to prevent recurrence.

Presentation Date


Actinomyces Israelii – A Rare Cause of Bacterial Peritonitis