Arcanobacterium haemolyticum osteomyelitis and sepsis: a diagnostic conundrum

Arcanobacterium haemolyticum can cause severe systemic infections and sepsis. Thus, accurate and timely identification of the organism is essential.

Case report and review of the pertinent English-language literature.

A 74-year-old male underwent repetitive surgical debridement and grafting for a full-thickness ulcer on the plantar surface of the left foot. One week after the last debridement, the patient presented to the emergency department with fever, hypotension, and severe left foot pain. A radiograph showed a soft-tissue defect of the plantar aspect of the left midfoot with gas along the lateral aspect of the fifth metatarsal. A below-knee amputation was performed. Blood culture and intraoperative tissue specimens grew colonies that exhibited β-hemolysis on sheep blood agar and agglutinated with streptococcal B group antiserum. However, gram staining revealed that the organism was a gram-positive bacillus, and a reverse Christie, Atkins, Munch-Peterson (CAMP) test showed that the organism inhibited the β-hemolysis of Staphylococcus aureus on sheep blood agar. Biochemical testing identified the organism as A. haemolyticum.

It is important to investigate for A. haemolyticum when organisms with β-hemolytic activity react with group B streptococcal antiserum. Otherwise, A. haemolyticum can be mis-identified as group B Streptococcus or Listeria monocytogenes. This distinction is important clinically, because despite good in vitro activity of penicillin (a first-line antibiotic for group B Streptococcus infections), treatment failures have been reported when penicillin has been used for A. haemolyticum infections.