Drug Resistance and Molecular Typing Characteristics of Diarrheagenic Escherichia coli in Patients with Diarrhea in Chifeng, China.

Diarrheagenic Escherichia coli (DEC) can cause diarrhea and other gastrointestinal diseases, leading to severe dehydration, malnutrition, and even death. The increasing drug resistance and the emergence of multidrug-resistant bacteria present significant challenges to the public health. This study employed qPCR detection, the broth microdilution method, and pulsed-field gel electrophoresis (PFGE) technology to analyze virulence gene, drug resistance, and phylogenetic relationships in DEC isolated from 1,000 stool samples of patients with diarrhea in Chifeng City from 2021 to 2024. A total of 96 strains of DEC were detected, yielding a detection rate of 9.6%. Among these, enteroaggregative E. coli (EAEC) comprised 72.9% (70 strains), enteropathogenic E. coli accounted for 26.0% (25 strains), and enterohemorrhagic E. coli constituted 1.1% (1 strain). The resistance rates of DEC to tetracycline (TET), ampicillin, nalidixic acid, sulfamethoxazole, and streptomycin were recorded at 60.4%, 57.3%, 51.0%, 49.0%, and 42.7%, respectively, with 51.1% of DEC strains exhibiting multidrug resistance. The PFGE banding patterns of the 96 DEC strains were highly polymorphic, with similarity coefficients ranging from 33.6% to 100.0%. Notably, a higher similarity coefficient indicated greater similarity in drug resistance phenotypes among the strains. These results indicate that the predominant type of DEC infection in patients with diarrhea in Chifeng City is EAEC, with a TET resistance rate as high as 60.4%. Furthermore, the resistance spectrum is broad, and the DNA level exhibits significant polymorphism.