Emergence of Clinical Clostridioides difficile Isolates With Decreased Susceptibility to Vancomycin

Area of Science:

• Infectious Diseases
• Microbiology
• Antimicrobial Resistance

Background:

• Clostridioides difficile infection (CDI) is a major cause of hospital-associated diarrhea and mortality worldwide.
• Vancomycin is a primary antibiotic treatment for both nonsevere and severe CDI cases.
• The emergence of antibiotic-resistant strains poses a significant public health threat.

Purpose of the Study:

• To investigate the prevalence of vancomycin and metronidazole nonsusceptible Clostridioides difficile strains in patient populations.
• To assess the clinical implications of vancomycin nonsusceptibility in a CDI mouse model.

Main Methods:

• Collected stool samples from CDI patients in Houston, Texas (n=438) and Nairobi, Kenya (n=98).
• Utilized broth dilution, Etest, PCR, and whole-genome sequencing to identify and characterize C. difficile isolates.
• Employed a CDI mouse model to evaluate vancomycin treatment efficacy against nonsusceptible strains.

Main Results:

• High rates of vancomycin nonsusceptibility were observed in both locations: 26% in Houston and 67% in Nairobi.
• Metronidazole nonsusceptibility was also prevalent (29% in Houston, 85% in Nairobi).
• Vancomycin treatment failed to clear infection in a mouse model infected with a vancomycin nonsusceptible strain, and vanA genes were absent.

Conclusions:

• Vancomycin-nonsusceptible C. difficile strains are actively circulating in patient populations.
• The increasing resistance to vancomycin presents a critical therapeutic challenge for CDI management.
• Routine antimicrobial susceptibility testing for C. difficile may be essential for effective treatment strategies.