A case of recurrent acute cholecystitis caused by Actinomyces odontolyticus , rare actinomycosis

Backgrounds Actinomyces species are gram-positive, obligate anaerobic rods and are rare causes of cholecystitis. Because Actinomyces species are anaerobic bacteria, it is difficult for Actinomyces to survive in bile apart from A. naeslundii. We experienced a case of recurrent acute cholecystitis caused by A. odontolyticus. Case presentation A patient had been diagnosed with acute cholecystitis and treated one month before and after that, admitted to our hospital because of recurrent cholecystitis. Gram stain of the bile revealed gram-positive rods and gram-positive cocci. We found A. odontolyticus and MRSA in bile culture and MRSA in blood culture. We administered piperacillin-tazobactam and then changed it to ampicillin-sulbactam and vancomycin. The patient underwent laparoscopic cholecystectomy and was discharged safely. Conclusions To our knowledge, this is the first case of cholecystitis caused by A. odontolyticus . Cholecystitis caused by Actinomyces species is rare. In addition, we may overlook it with the low positivity of bile cultures of Actinomyces . Whenever the cholecystitis recurs without any obstruction of the biliary tract, we should search for the gram-positive rods hidden in the bile, such as A. odontolyticus, as the causative organism, even if the bile culture is negative.