Validation of a clinical scoring system to differentiate mycobacterial and bacterial causes of spondylodiscitis: a retrospective cohort study from Kerala, India

Background: Mycobacterial and bacterial spondylodiscitis require distinct therapeutic approaches. However, microbiological diagnosis is often delayed or unavailable in resource-limited settings. This study aimed to validate a clinical scoring system developed in a prior retrospective cohort study in Karnataka (India) to differentiate these aetiologies. Methods: We conducted a retrospective cohort study of patients with microbiologically confirmed spondylodiscitis admitted between January 2017 and August 2024 in a tertiary care centre in Kerala, India. Demographic, clinical, laboratory, imaging, and treatment data were compared between the two groups, and the scoring system’s diagnostic performance was assessed. Results: Of 151 patients with infectious spondylodiscitis, 73 patients with community-acquired microbiologically confirmed infection were included. Of these, 32 (44%) had mycobacterial, and 41 (56%) had bacterial spondylodiscitis [Staphylococcus aureus (37%), Escherichia coli (11%), Klebsiella pneumoniae (11%), Streptococcus spp (4.1%), Salmonella spp (1.4%)]. The scoring system demonstrated good diagnostic accuracy for bacterial aetiology (AUC: 0.78; 95% CI: 0.67–0.88). Mycobacterial cases were younger, had longer symptom duration, lower C-reactive protein and leukocyte counts, and more frequent vertebral height loss on imaging. The rate of clinical improvement was similar between groups. Conclusions: The validated clinical scoring system reliably distinguishes mycobacterial from bacterial spondylodiscitis and may guide empirical management in settings where timely microbiological diagnosis is not feasible.