Objective To investigate the pathogenic spectrum and molecular characteristics of infectious diarrhea among children in Putuo District of Shanghai from 2018 to 2023， and to provide scientific basis for the prevention and control of infectious diarrhea in children.

Methods Fecal samples from the cases visited sentinel hospitals for children’s diarrheal disease in Putuo District， Shanghai， were collected from January 2018 to December 2023. A total of 11 species of bacteria were isolated and cultured， and 5 species of viruses were detected by real-time fluorescent polymerase chain reaction （PCR）. The molecular typing of some positive strains was analyzed by the standard pulsed-field gel electrophoresis （PFGE） method. The polymerase-capsid protein linkage region of some norovirus-positive samples was amplified by reverse transcription PCR， and was sequenced and analyzed by bioinformatics software. The Chi-square test and Fisher’s exact probability test were used to compare the pathogen-positive rates in 2018‒2019 and 2020‒2023.

Results Of the 707 cases of children with infectious diarrhea， the total positive rate was 47.67%， with a single bacterial positivity rate of 16.27%， a single viral positivity rate of 22.63%， and a mixed positivity rate of 8.77%， respectively. The dominant pathogens were rotavirus （10.75%）， norovirus （10.33%）， enteropathogenic Escherichia coli （8.06%）， Salmonella （6.36%）， enteroaggregative Escherichia coli （5.52%）， and Campylobacter （5.23%）. Bacterial infections were predominant in summer and fall， and viral infections were predominant in winter and spring. The total positive rate decreased in 2020‒2023 compared with that of 2018‒2019 （χ²=5.753，P<0.05）. Thirty-seven strains of Salmonella， 81 strains of diarrheagenic Escherichia coli，and 19 strains of Campylobacter were completed for the molecular typing analysis by PFGE， which were classified into 28， 80 and 18 banding types， respectively， with a wide range of banding similarity. Nineteen copies of norovirus GⅡ group gene sequences were analyzed and classified into 5 genotypes， which were mainly GⅡ.Pe-GⅡ.4 and GⅡ.P16-GⅡ.2 types.

Conclusion Rotavirus， norovirus， diarrheagenic Escherichia coli， Salmonella， and Campylobacter are the dominant pathogens of infectious diarrhea in children in Putuo District of Shanghai. The pathogen spectrum shows a trend of seasonal epidemic characteristics， with a diversity of molecular characteristics of some pathogens. Surveillance and monitoring on molecular characteristics of the pathogens of infectious diarrhea in children should be strengthened in different seasons， so as to provide a laboratory basis for the prevention and control of infectious diarrhea.