Abstract / Summary
Clostridium perfringens is an important toxin-producing pathogen associated with a range of infections in humans and animals. Although its toxins are recognized as major virulence determinants, the extent to which toxin-mediated effects account for host responses during infection remains unclear. In this study, we used Caenorhabditis elegans as an in vivo model to compare the physiological and molecular responses elicited by whole-cell C. perfringens and its cell-free supernatant (CFS). The C. perfringens isolate obtained from the gastrointestinal tract of patients diagnosed with IBD was characterized and evaluated for pathogenicity in C. elegans . The CFS was prepared and validated functionally through hemolytic activity, heat-inactivation and dose-dependent toxicity assays. Host responses were assessed using lifespan, pharyngeal pumping, egg laying and microscopic analyses. Transcriptional changes were analysed by quantitative RT-PCR, keeping pmp-3 as the reference gene. Exposure to both whole bacterial cells and the CFS significantly impaired the survival, feeding behaviour, and reproductive capacity of C. elegans . However, the magnitude of these effects was greater during whole-cell exposure. The molecular study assessed the expression of genes associated with host defence and stress responses, including sek-1 and pmk-1 associated with p38 MAPK signalling, and the antimicrobial response marker lys-7 . skn-1 and gst-4 are associated with stress and detoxification responses, together with the oxidative-stress marker sod-3. Whole-cell exposure showed greater relative expression of sek-1 , pmk-1 , and lys-7 , compared with CFS treatment. Similarly, skn-1 and gst-4 were more highly expressed following whole-cell exposure than CFS treatment, while the oxidative-stress marker sod-3 was strongly induced by whole-cell exposure but showed minimal change following CFS treatment. These results suggest that while the toxin-associated components present in the CFS may contribute to the observed host responses, they cannot recreate responses observed during whole-cell exposure. This study also showed that C. elegans proved to be a useful model to evaluate the potential contribution of bacterial toxins to the development of infection and disease.