A combination of surgical and medical treatment is normally required for patients with septic arthritis(1). Antibiotics
selected for use on these patients are normally based on tissue culture results(2). However, in sub-acute and chronic septic arthritis cases, the results of the culture are usually negative as a result of prior treatment. The present study will investigate the incidence of culture-negative septic arthritis and the outcomes based on the use of first-line drug antibiotics for the treatment of sub-acute and chronic septic arthritis. For the present study, the authors retrospectively reviewed medical records of surgically treated septic arthritis cases over the past 10 years at Siriraj Hospital. The patient culture results, the antibiotics used, and the results of treatment were all recorded and analyzed.
One hundred fifty-three septic arthritis patients were reviewed. Sixty-two patients were classified as having been
diagnosed with either sub-acute or chronic septic arthritis. Thirty-six of 62 patients (58.1%) had a negative culture result. In the culture-positive patients, 42.3% had Streptococcus, 26.9% had Staphylococcus aureus, 11.5% had other gram positive bacteria, 15.4% had gram-negative bacteria, and 3.8% had tuberculus infection. In the culture-negative sub-acute and chronic group (36 of 62), 23 patients received Cefazolin, nine patients received Cloxacillin, and four patients received Clindamycin. Successful results were 69.9%, 66.7% and 75%, respectively. The present study reflects that the incidence of culture-negative, sub-acute and chronic septic arthritis is approximately 58.1%. The first-line class of antibiotics remains the appropriate antibiotic choice for these patients because they are still effective for treatment of septic arthritis in up to 70% of all cases.

Keywords: Septic arthritis, Culture negative, Antibiotic, Chronic septic arthritis