Abstract: Objective To study the species distribution of pathogenic bacteria in children with bacterial diarrhea in Chongqing in the past 27 years, and to provide scientific basis in prevention and treatment of children's bacterial diarrhea in Chongqing.Methods A retrospective study was conducted on the bacterial culture-positive strains of fecal specimens from hospitalized children with diarrhea from January 1, 1991 to December 31, 2017.During the same hospitalization period of the same child, if fecal specimens were sent for multiple times and the same strain was isolated, only the first record was included for analysis.The gender, age, living environment of the children, and the type and time of detection of positive pathogenic bacteria in fecal specimens were selected.Results 2,409 strains of pathogenic bacteria were isolated from 33,957 fecal specimens of children with diarrhea during the past 27 years, with the total detection rate being 7.09%, including Shigella spp.(78.83%, 1,899/2,409),mainly Shigella flexneri (87.36%,1,659/1,899), of which S.flexneri Type Two was more common (97.17%,1,612/1,659);Salmonella spp.(13.24%,319/2,409), mainly Salmonella typhimurium(69.28%,221/319); Diarrheal escherichia coli(5.06%,122/2,409),mainly pathogenic E.coli(77.05%,94/122).In terms of the detection period, the detection rate was the highest in 1995, which was 27.67%(249/900). Before 2000 (except 1992), the detection rate was >10%, and after 2000, it fell to below 5%;The number and detection rate of pathogenic bacteria were the highest in August, September and October. From the year 1991 to 1999 (n=1,860), the year 2000 to 2008 (n=348), and the year 2009 to 2017 (n=201), the proportion of S.flexneri Type Two was decreased from 80.48% to 0,and the proportion of Salmonella typhimurium increased from 4.35% to 58.71%. The proportion of Salmonella typhimurium in infants was the highest (29.58%), and the proportion of S.flexneri Type Two was the highest in other age groups.Conclusion The dominant pathogenic bacteria species causing bacterial diarrhea in children was S.flexneri Type Two in the early time period (from the year 1991 to 1999), while Salmonella typhimurium was more predominant in late time period (from the year 2009 to 2017).

Key words: Bacterial diarrhea, Chlidren, Pathogenic bacteria