First Reported Case of Prosthetic Joint Infection Caused by an Unusual Bacterium: Neisseria macacae.

Acute non-traumatic joint pain, swelling, and fever require prompt evaluation for a prosthetic joint infection, a serious bacterial complication affecting both large and small joints. Neisseria gonorrhoeae and Staphylococcus aureus are among the most common causes, typically involving a single joint. To the best of our knowledge, we report the first case of a prosthetic joint infection caused by Neisseria macacae, highlighting its relevance for differential diagnosis. Identification was achieved using MALDI-TOF and confirmed with next-generation sequencing. While N. gonorrhoeae and Neisseria meningitidis are well-recognized pathogens, other Neisseria species may cause opportunistic infections, underscoring the importance of comprehensive microbiological evaluation.