Microbiological spectrum of septic arthritis: Diagnostic insights and clinical implications

Septic arthritis is an orthopaedic emergency characterised by inflammation of joint constituents due to infectious aetiology. Delayed diagnosis can lead to irreversible joint damage. This study aimed to isolate and characterise the bacteria causing septic arthritis and study their clinical and laboratory profile.

This was a cross-sectional study conducted in the department of Microbiology, of a tertiary care hospital, from June 2023 to November 2024. Intra articular specimens obtained aseptically from clinically suspected cases of septic arthritis were subjected to microscopy, aerobic and anaerobic cultures and culture on Lowenstein-Jensen medium and cartridge based nucleic acid amplification test (CB-NAAT) for Mycobacterium tuberculosis. Bacterial isolates were identified using matrix-assisted laser desorption ionisation-time of flight mass spectrometry (MALDI-ToF). Antibiotic sensitivity testing was done by the Vitek-2 compact system and interpreted according to CLSI guidelines 2023. Clinical history, including risk factors, treatment and surgical interventions, were collected and infective markers like total leukocyte count, C- reactive protein (CRP), erythrocyte sedimentation rate (ESR) and synovial fluid cytology were analysed. Statistical analysis was performed using SPSS version 29.

Out of the total 76 samples, bacterial pathogens were detected in 32 (42.1%). Among the 32 cases; aerobic culture yielded 29 (90.62%) isolates, 1 (3.12%) by anaerobic culture, and 2 (6.25%) by CB-NAAT. Staphylococcus aureus was the most common pathogen isolated (9, 28.12%) and all were susceptible to clindamycin, vancomycin, teicoplanin and linezolid. Out of the total 76 patients, 66 (86.84%) cases accounted for native joint septic arthritis, while 10 (13.15%) had prosthetic joint infections. Prior joint surgery was found to be the most common risk factor. ESR was significantly higher in microbiologically confirmed cases (p = 0.032) CONCLUSION: Septic arthritis exhibits a diverse bacterial aetiology, with S. aureus being the predominant. Although uncommon, anaerobes and Mycobacterium tuberculosis should be considered. Antibiotic sensitivity testing remains crucial for guiding the right antimicrobial therapy.