Objective: To describe a case of severe sepsis, cavitary pneumonia, and pyomyositis caused by Arcanobacterium haemolyticum.
Case summary: An 18-year-old male with a medical history significant for mild asthma presented to the emergency department complaining of a 7-day history of fever, diffuse myalgias, nausea, vomiting, diarrhea, and pain in his right upper quadrant, right shoulder, and left thigh. Cultures of blood, bronchoalveolar fluid, and surface and surgical swabs from the patient's left lower extremity grew A. haemolyticum. The patient was successfully treated with intravenous penicillin G 4 million units every 4 hours and azithromycin 500 mg once daily for 14 days. Within 36 hours after initiation of focused therapy, he became afebrile, pain decreased, and pulmonary symptoms abated. Oral azithromycin 500 mg/day for an additional 3 weeks was prescribed on discharge, and the patient showed no relapse at 2-month follow-up.
Discussion: A. haemolyticum is a weakly acid-fast, branching gram-positive bacillus most commonly implicated in pharyngitis in healthy adolescents and skin and soft-tissue infections in older, immunocompromised patients. Systemic infections are rarely reported in the literature. This organism remains susceptible to most classes of antimicrobials, including penicillins, cephalosporins, carbapenems, macrolides, tetracyclines, clindamycin, and vancomycin. Routine resistance has been reported only with trimethoprim/sulfamethoxazole.
Conclusions: To our knowledge, there are no published case reports of severe sepsis caused by A. haemolyticum. While treatment options are numerous, we recommend the use of intravenous penicillin or a cephalosporin as first-line pharmacologic management of deep-seated infections caused by this rare organism.