Case Report: First report of chronic osteomyelitis caused by Staphylococcus hyicus: a zoonotic pathogen with underreported clinical significance

Abstract

<ns3:p> Background <ns3:italic>Staphylococcus hyicus</ns3:italic> is a zoonotic pathogen primarily associated with animal infections. Human infections are exceedingly rare, with only six cases documented in the literature. The pathogen’s role in chronic osteomyelitis of long bones has not been previously reported, presenting unique diagnostic and therapeutic challenges. Case Report We report the first case of chronic osteomyelitis of long bones caused by methicillin-resistant <ns3:italic>S. hyicus</ns3:italic> in a 34-year-old male farmer with a history of recurrent osteomyelitis following trauma and livestock exposure. The patient presented with purulent discharge from two fistulae on the medial aspect of the right thigh. Imaging studies revealed bony sequestration, periosteal reaction, and multiple fistulous tracts consistent with Cierny-Mader stage III chronic osteomyelitis. Microbiological identification of coagulase-negative methicillin-resistant <ns3:italic>S. hyicus</ns3:italic> was achieved via culture and phenotypic analysis of aspirates from the fistulae and intraoperative samples, with confirmation via matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). A multidisciplinary treatment strategy was implemented, combining extensive surgical debridement and dead space management with a 24-week tailored antibiotic regimen. The regimen included intravenous teicoplanin and ciprofloxacin for 14 days, followed by oral ciprofloxacin and cotrimoxazole. The patient achieved sustained remission with no recurrence at 2.5 years of follow-up. Conclusion This case underscores the zoonotic potential of <ns3:italic>S. hyicus</ns3:italic> and highlights its capacity to cause severe, persistent infections in humans, particularly in individuals with occupational or environmental exposure to livestock. Advanced diagnostic techniques such as MALDI-TOF MS are essential for accurate identification, mitigating the risk of misdiagnosis due to phenotypic similarities with other staphylococcal species. Clinicians should consider <ns3:italic>S. hyicus</ns3:italic> in the differential diagnosis of chronic osteomyelitis in patients with relevant exposure histories to enable timely and targeted therapeutic interventions. </ns3:p>