Humoral immune response to <i>C. kefirresidentii</i> and <i>S. epidermidis</i> as pathobiotic components of tuberculosis foci

The role of lung microbiota in tuberculosis has attracted increasing attention, particularly in the context of its interaction with the immune system and its contribution to systemic chronic inflammation. Microorganisms constituting the local microbial environment of tuberculosis lesions may not only generate specific immune signals but also participate in the immunopathogenesis of infection through cross-interactions with the host immune system. In a previously conducted large-scale microbiological screening of facultative anaerobic microbiota in tuberculosis lesions, we isolated two bacterial strains – Corynebacterium kefirresidentii and Staphylococcus epidermidis – from the caseous material of tuberculomas. Based on their microbiological and biochemical characteristics, as well as identified resistance to several first-line antituberculosis drugs, these microorganisms are considered elements of the pathobiota that may contribute to the maintenance of local inflammation in tuberculosis. Cell lysates of these microorganisms were used as sources of potential antigens to assess immune responses. In the present study, a laboratory approach was developed and tested to comparatively evaluate the humoral immune response to components of nonspecific microbiota associated with tuberculosis lesions. The analysis was carried out using a semi-quantitative ELISA with blood serum samples obtained from patients with pulmonary tuberculosis (n = 90) and healthy donors (n = 90). Seroprevalence and levels of specific IgG against C. kefirresidentii were significantly higher in tuberculosis patients compared to the control group (p 0.05), suggesting a possible involvement of this microorganism in the immunopathogenesis of the disease. In contrast, no statistically significant differences were observed between groups for S. epidermidis, which is likely related to its high prevalence in the general population as a common skin commensal. Although the role of immune responses to S. epidermidis in tuberculosis has not been previously considered, some studies indicate the involvement of certain strains in the pathogenesis of common dermatological disorders. A positive correlation between antibody levels to both microorganisms, observed only in tuberculosis patients (p = 0.001), may indicate a pathological nature of immune interactions in pulmonary tuberculosis. These findings highlight the importance of evaluating humoral responses to microbiota components in the context of tuberculosis and expand our understanding of immune mechanisms accompanying this infectious process.