Haemophilus influenzae Acute Prosthetic Joint Infection: A Rare Case Report on Time-Critical, Pathogen-Specific Management.

Introduction: Prosthetic joint infections (PJIs) are a serious complication of arthroplasty, often necessitating prolonged therapy and revision surgeries. Haemophilus influenzae is an uncommon cause of PJI, especially in immunocompromised individuals and individuals with co-morbidities. Its fastidious nature frequently leads to negative cultures, delaying diagnosis and targeted therapy.

Case Report: We report the case of a 52-year-old male with rheumatoid arthritis on immunosuppressive therapy, who presented with acute right hip pain, swelling, and purulent wound discharge 3 months after revision total hip arthroplasty. Initial workup revealed elevated inflammatory markers and signs of joint infection (JI). Conventional microbiological methods including Gram stain, acid-fast bacilli testing, and enrichment cultures were inconclusive. However, syndromic multiplex polymerase chain reaction (PCR) using the BioFire® JI panel detected H. influenzae within 2 h of intraoperative sample collection. The patient underwent debridement, targeted antibiotic therapy, and implant retention (DAIR). Empirical therapy with meropenem and vancomycin was promptly de-escalated to intravenous ceftriaxone, based on PCR results. Clinical recovery was marked by rapid decline in C-reactive protein, resolution of symptoms, and a successful switch to oral therapy. At 6-week and 16-week follow-up, the patient was asymptomatic, with normal inflammatory markers and radiographs, and a functioning retained implant.

Conclusion: This case underscores the clinical value of rapid syndromic testing in detecting rare, fastidious pathogens like H. influenzae in PJIs. The early identification facilitated timely DAIR, targeted antibiotic therapy, reduced hospital stays, and preserved the implant. The approach highlights the role of molecular diagnostics in enhancing antimicrobial stewardship and improving clinical outcomes in complex orthopedic infections.