Molecular Epidemiology of Type F Among Diarrheal Patients and Virulence-Resistance Dynamics - 11 Provinces, China, 2024.

Introduction: Type F () represents a significant pathogen in human gastrointestinal diseases, primarily through its gene encoding enterotoxin (CPE). This investigation examined the prevalence, antimicrobial resistance patterns, and genetic characteristics of Type F within the Chinese population.

Methods: The study analyzed 2,068 stool samples collected from 11 provincial hospitals in 2024. Antimicrobial susceptibility testing was conducted following Clinical & Laboratory Standards Institute (CLSI) guidelines, while whole-genome sequencing provided detailed genetic profiles. Evolutionary relationships and clonal transmission patterns were investigated through phylogenetic and genetic environment analyses.

Results: The prevalence of Type F was 2.38%, with isolates predominantly identified in human clinical samples and higher detection rates in gastroenterology departments. Notably, 47.1% of isolates demonstrated high resistance to metronidazole, while all exhibited intermediate resistance to erythromycin. Phylogenetic analysis revealed high similarity among isolates from patients within the same province (single-nucleotide polymorphism (SNPs)<100), and genetic environment analysis indicated potential horizontal gene transfer between animal and human strains.

Conclusions: This investigation predominantly identified Type F in human clinical cases, with sporadic detection in pets and food products. These findings highlight the emergence of Type F outbreaks among diarrheal patients, emphasizing the necessity for targeted interventions as virulence factors increase.