Objective:To identify candidate strains of Nontoxigenic Clostridioides difficile (NTCD) with potential for intervention in Clostridioides difficile infection (CDI) and analyze their phenotypic characteristics. Methods:A total of 713 Clostridioides difficile strains from various sources were systematically collected nationwide between 2015 and 2023. This included 649 strains isolated from human fecal samples and 64 strains isolated from the fecal samples of farmed animals. NTCD strains were preliminarily screened through toxin gene detection and antibiotic sensitivity test, and then NTCD candidate strains with potential for intervention in CDI were screened by a series of in vitro experiments, including MLST, sporulation, germination, adhesion, motility, and biofilm formation ability. Ultimately, the virulence genes and antimicrobial resistance genes of the candidate strains were comprehensively analyzed to rigorously assess their safety profiles. Results:Among 713 strains of C. difficile from different sources, 10 strains were initially screened out, which were non-toxin-producing and sensitive to antibiotics. MLST showed that seven strains were from the Clade1 branch and three strains were of a novel type. The results of sporulation and germination showed that SD59, SD178, SJZ17, and WZ142 had stronger sporulation and germination abilities. The adhesion of 10 strains was high, and the adhesion rate was between 72.93% and 99.32%. The motility of all strains was different, and the motility of SD178, SD59 and SJZ17 was stronger. The biofilm-forming ability of all strains was weak. SD59, SD178 and SJZ17 carried a limited number of virulence and resistance genes, thereby posing a relatively low safety risk. Conclusion:Three NTCD strains are successfully selected as potential effective NTCD strains to interfere with CDI.

Objective:To identify candidate strains of Nontoxigenic Clostridioides difficile (NTCD) with potential for intervention in Clostridioides difficile infection (CDI) and analyze their phenotypic characteristics. Methods:A total of 713 Clostridioides difficile strains from various sources were systematically collected nationwide between 2015 and 2023. This included 649 strains isolated from human fecal samples and 64 strains isolated from the fecal samples of farmed animals. NTCD strains were preliminarily screened through toxin gene detection and antibiotic sensitivity test, and then NTCD candidate strains with potential for intervention in CDI were screened by a series of in vitro experiments, including MLST, sporulation, germination, adhesion, motility, and biofilm formation ability. Ultimately, the virulence genes and antimicrobial resistance genes of the candidate strains were comprehensively analyzed to rigorously assess their safety profiles. Results:Among 713 strains of C. difficile from different sources, 10 strains were initially screened out, which were non-toxin-producing and sensitive to antibiotics. MLST showed that seven strains were from the Clade1 branch and three strains were of a novel type. The results of sporulation and germination showed that SD59, SD178, SJZ17, and WZ142 had stronger sporulation and germination abilities. The adhesion of 10 strains was high, and the adhesion rate was between 72.93% and 99.32%. The motility of all strains was different, and the motility of SD178, SD59 and SJZ17 was stronger. The biofilm-forming ability of all strains was weak. SD59, SD178 and SJZ17 carried a limited number of virulence and resistance genes, thereby posing a relatively low safety risk. Conclusion:Three NTCD strains are successfully selected as potential effective NTCD strains to interfere with CDI.

Objective:To understand molecular characteristics and antibiotic resistance of Clostridioides ( C.) difficile isolated from children in China, and provide data support the development of disease risk assessment and burden studies. Methods:A total of 155 strains of C. difficile isolated from children aged <12 years in 14 provinces (autonomous regions, municipalities) in China from 2010 to 2023 were used for the analyses on molecular characteristics and antibiotic resistance of C. difficile by PCR and drug susceptibility test. Results:A total of 26 sequence types (STs) and 18 ribotypes (RTs) were identified in the 155 C. difficile isolates, in which ST3 (20.65%), ST54 (16.13%), ST35 (12.90%), and RT012/ICDC007 (14.84%), RT001/ICDC001 (11.61%), RT046/ICDC018 (8.39%) were the most common. One highly virulent strain with RT078 and 27 non-toxin-producing strains were also found; the predominant toxin gene was tcdA+ tcdB+ cdt-. All the strains were sensitive to metronidazole and vancomycin, and there were 29 multidrug-resistant strains, in which 1 strain was resistant to all the seven antibiotics except for vancomycin and metronidazole. Conclusions:Molecular characteristics and antibiotic resistance of C. difficile in children were similar to those in whole population in China, but there were regional distribution differences. It is necessary to strengthen the routine drug-resistance surveillance for C. difficile infection in children in China.