A 57 year old immunocompetent man with no significant past medical history sustained a dog bite injury to his left index finger. He first presented to his local primary care immediately after the injury and was prescribed a course of oral amoxicillin-clavulanic acid. Despite receiving additional empirical oral antibiotics, there was minimal clinical improvement.
He was referred by his general practitioner a month after the injury with clinically and radiologically evidence of osteomyelitis of the distal and middle phalanx. However, he delayed his care due to personal circumstances and a complex social history.
At six weeks post-injury, he presented to the Plastic and Reconstructive Surgery Unit, where he underwent surgical debridement and terminalization of the index finger to the proximal phalanx. Bone biopsy demonstrated growth of Schaalia Canis—marking the first documented human infection caused by this organism in Australia. Infectious disease team were consulted and a recommendation made for the initiation of intravenous meropenem with oral amoxicillin-clavulanic acid tail for 6 weeks in total.
Dog bite injuries are polymicrobial, with microbiological specimens typically growing Pasteurella canis, Pasteurella multocida, Streptococcus spp. and Staphylococcus spp. Empirical antibiotic therapy with amoxicillin-clavulanate is widely recommended due to its broad-spectrum coverage against these organisms. However, in this case, oral antibiotics failed to resolve the infection, likely due to the deep-seated bacterial inoculation, leading to osteomyelitis.
This case underscores the limitations of standard empirical antibiotic therapy in deep infections and highlights the potential for atypical zoonotic pathogens, such as Schaalia canis, in dog bite injuries. Clinicians should maintain a high index of suspicion for uncommon organisms when managing complicated infections following animal bites.