Treatment of septic arthritis

[The authors respond:]

We thank Cheryl Main for her comments on the antimicrobial coverage for both gram-positive and gram-negative septic arthritis that we recommended in our article.¹ Our review focused on nongonococcal septic arthritis in patients with pre-existing inflammatory arthritis, and space constraints meant that we could not elaborate on many special circumstances.

Unfortunately, the literature on community-acquired gram-positive septic arthritis in this population is limited. One case series of 59 patients with septic arthritis (in which 15 of the cases were due to MRSA and 44 were not) includes several patients with pre-existing rheumatic disease but does not provide details on the nature of their rheumatic disease.² The authors of this case series suggest considering empiric treatment for MRSA infection in patients with septic arthritis if there are risk factors such as recent admission to hospital, known infection or colonization with MRSA, multiple comorbidities in addition to the rheumatic disease, injection drug use or residence in communities known to have a high prevalence of community-acquired MRSA infections. These suggestions are consistent with our interpretation of the guidelines referenced by Main.^3,4 Hawkes suggests that people of First Nations or African-American heritage, athletes who participate in contact sports, injection drug users, men who have sex with men, military personnel, inmates of correctional facilities, veterinarians, pet owners and pig farmers may be at increased risk of developing MRSA infections.³ As a result, our recommendations continue to be to use cefazolin empirically. For patients known to have risk factors for MRSA infections, vancomycin should be included in the treatment plan until the organism's susceptibility is established.

Although gram-negative infections occur less frequently than gram-positive infections, they are important and potentially difficult to treat. Although it was not the focus of our review, gonococcal septic arthritis should be considered in patients who have demographic risk factors for this condition or in whom Gram's staining does not show bacteria.