A 30-year-old Caucasian man with a history of uncontrolled diabetes mellitus complicated by peripheral neuropathy, diabetic foot ulcers, methicillin-resistant S. aureus (MRSA) osteomyelitis and amputation of the left 2nd distal phalanx presented to Wound Clinic with a malodorous, painful plantar ulcer. The patient had been followed in Wound Clinic after sustaining foot trauma from a falling tree 3 months earlier while in rural Michigan. Physical exam revealed normal vitals and an erythematous, edematous distal left foot with a 3cm x 0.5cm x 2mm plantar ulcer with necrotic tissue and serosanguinous drainage. Laboratory studies were remarkable for no leukocytosis, but elevated inflammatory markers. Left foot X-ray showed amputation of the second distal phalanx, soft tissue swelling and indistinctness of the cortex of the 3rd distal phalanx, consistent with osteomyelitis. On day of admission, he underwent intraoperative debridement and resection of the distal 2nd metatarsophalangeal joint. Post-operative antibiotics included vancomycin and cefepime. On post-op day 3, intraoperative wound and bone cultures were reported as growing aerobic gram-positive bacilli, few diphtheroids, and coagulase-negative staphylococcus. By post-op day 6, histochemical analyses confirmed the presence of Arcanobacterium haemolyticum.
A. haemolyticum (previously Corynebacterium haemolyticum), a facultative aerobic gram-positive rod, was first isolated from United States servicemen and indigenous populations of the South Pacific in 1946. Early reported cases detailed A. haemolyticum as a causative pathogen for exudative pharyngitis (most commonly in adolescents) and cutaneous infections. A. haemolyticum infections can be separated epidemiologically into 2 distinct subsets: healthy adolescents presenting with upper respiratory tract infections and immunocompromised patients presenting with systemic, more serious infection. The organism has been identified in severe infections such as vertebral osteomyelitis, endocarditis, brain abscess, and Lemierre disease. Osteomyelitis caused by A. haemolyticum has been described in less than 5 cases in the literature. A. haemolyticum may be overlooked or misdiagnosed due to its slow growth and features similar to other pathogens. Initial microbiology reads that show mixed flora, including gram-positive rods and diphtheroid bacilli, are part of the normal flora of the skin. A. haemolyticum’s distinct colony features typically are only seen after 72 hours of incubation.
Gram-positive organisms, including Staphylococcus aureus, β hemolytic Streptococcus, and coagulase-negative Staphylococcus are the most common cause of osteomyelitis. A. haemolyticum is another gram-positive organism and causative agent of osteomyelitis that is often overlooked or misdiagnosed. Differentiation of A. haemolyticum from other gram-positive organisms is essential for proper management and appropriate antibiotic treatment.
To cite this abstract:Lesky L, Camba J, Alzahrani T, Santos S, Fortenko A. Blood, Brain, and Now Bone – Learning More About an Often Overlooked Pathogen. Abstract published at Hospital Medicine 2015, March 29-April 1, National Harbor, Md. Abstract 469. Journal of Hospital Medicine. 2015; 10 (suppl 2). https://www.shmabstracts.com/abstract/blood-brain-and-now-bone-learning-more-about-an-often-overlooked-pathogen/. Accessed July 20, 2019.