Linked mutations within the pathogenicity locus of increase virulence.

Background: The clinical manifestations of infections range from diarrhoea to pseudomembranous colitis (PMC) and death. We evaluated the association between gene content in clinical isolates and disease severity.

Methods: Fifty-three isolates were subjected to Sanger sequencing, clinical data were used to analyse the association of gene content with disease severity, and 83 non-duplicate isolates were collected to confirm the results. Virulence was further examined by functional and experiments.

Results: Among the 53  isolates, ribotypes 017 ( = 9, 17.0%) and 012 ( = 8, 15.1%) were predominant. Fifteen strains exhibited a correlation between mutations of pathogenicity locus genes (, , , and ) and were named linked-mutation strains. Ribotypes are not associated with clinical PMC and Linked-mutation strains. The proportion of patients with PMC was higher in the group infected with linked-mutation strains than in the non-linked-mutation group (57.14% vs. 0%,  < 0.001). The linked-mutation rate of was higher in patients with PMC than in patients without PMC (89.47% vs. 7.8%,  < 0.0001). Linked-mutation strains showed greater cytotoxicity and caused more severe tissue damage in a mouse model.

Conclusions: Linked-mutation strains are associated with high virulence and PMC development. This result will help monitor the clinical prognosis of infection and provide key insights for developing therapeutic targets and monoclonal antibodies.