Background The rising incidence of Salmonella septic arthritis in immunocompromised patients with serious complications, and high relapse rates, remains an unsolved clinical problem. Our previous IEM study suggested that quinolone compound antibiotics may enhance the intracellular killing function of the synovial mononuclear cells in those patients. This may help eradication of this organism from the joint at the early phase. However, the clinical outcome after long term antibiotic treatment has not been evaluated.

Objectives To evaluate the clinical outcome of Salmonella septic arthritis patients after long term antibiotic treatment.

Methods Clinical data of 13 patients with 19 episodes of culture proved group D or group B Salmonella septic arthritis were studied. Clinical outcomes after long term antibiotic treatment were only analysed in the patients who completed the treatment course and had at least 1 year follow up.

Results All 13 patients had underlying diseases, 12 had been treating with immunosuppressive drugs, except one case who had underlying OA. SLE was the most common underlying disease found in our study. Acute and chronic onset monoarthritis occurred in a similar numbers. Chronic long standing joint infection mostly occurred in the patients with partial response to the first line antibiotic treatment. Knee and hip joint were the common sites of infection. Arthroscopic drainage or arthrotomy was performed in all but one patient who was treated by repeated arthrocentesis of the knee joint. All patients received at least 2-week parenteral antibiotic. Three patients were excluded from antibiotic treatment evaluation because of lost follow up after being discharged from the hospital.

Clinical response at the early phase: In 16 events of Salmonella septic arthritis, 6 were treated with cotrimoxazole, 7 with quinolone compound and 3 with beta-lactam antibiotics. Dramatic clinical response was found only in the patients who were treated with cotrimoxazole or quinolone compound antibiotics. 2 out of 3 patients who were treated with beta lactam antibiotics partially responded to antibiotics given. After 8 weeks, these 2 patients were retreated with another course of cortimoxazole or quinolone compound.

Long term Clinical outcome: In all patients who were treated with 3 month course of quinolone compound, there was no relapse after 1–5 years follow up. Relapses were more common in cotrimoxazole treatment group (4 out of 6) and usually occurred within 4 months after antibiotic was stopped. Only one case was completely responded to beta-lactam antibiotic treatment without relapse. AVN was the most common complication found in Salmonella septic hip, and chronic osteomyelitis was found in a case with septic knee.

Conclusion We suggest to treat Salmonella septic arthritis in immunocompromised host with adequate drainage and 3 months of quinolone compound antibiotics. Alternative regimen is parenteral cotrimoxazole in an early phase followed by oral quinolone compound for totally 3 months. Long term treatment with cotrimoxazole frequently resulted in relapse.