Analysis of phenotypic and genotypic characteristics of Clostridioides difficile RT027/ST1 and RT017/ST37 mixed infection in a rare case.

OBJECTIVES

Mixed Clostridioides difficile infections refer to the simultaneous infection of the same host with strains of different genotypes. The incidence rate of such infections is relatively low, at approximately 8%. Cases of co-infection involving the highly toxigenic strain RT027/ST1 and the commonly prevalent strain in Asia, RT017/ST37, are even more rare. This case identified a patient with pulmonary tuberculosis and diarrhoea who was co-infected with Clostridioides difficile strains RT027/ST1 and RT017/ST37. A comprehensive analysis was performed to examine the phenotypic and genotypic characteristics of the co-infecting strains.

METHODS

Faecal specimens were collected from patients for the isolation and cultivation of Clostridioides difficile. Subsequently, six colonies were selected based on their morphological characteristics for subculturing. All strains were subjected to PCR-ribotyping and multilocus sequence typing (MLST). Antimicrobial susceptibility testing was performed using the agar dilution method. Whole genome sequencing was performed for the strains RT027/ST1 and RT017/ST37, and virulence factor loci along with antibiotic resistance associated genes were analysed.

RESULTS

Stool culture of Clostridioides difficile revealed the presence of two distinct colony morphotypes. MLST and PCR ribotyping revealed a mixed infection with C. difficile strains RT027/ST1 and RT017/ST37. Antibiotic susceptibility testing revealed that isolates showed strong drug resistance and subsystem analysis of whole genome sequencing revealed the presence of a substantial number of virulence factors and resistance genes associated with C. difficile RT027/ST1 and RT017/ST37.

CONCLUSION

Mixed Clostridioides difficile infections exhibit enhanced antimicrobial resistance, accompanied by an increased prevalence of virulence factors and resistance genes.