Abstract: Objective To study pathogenic spectrum of infectious diarrhea and its molecular biology characteristics.Methods Stool specimens were collected from patients with clinical diagnosis of infectious diarrhea at 5 sentinel disease surveillance hospitals in Tianjin city from 2007 through 2010 for detections of rotavirus(RV),norovirus(NV),Shigella,Escherichia coli,Salmonella,and other pathogens.Drug resistance of the isolated Shigella strains to 14 antibiotics frequently used in clinical treatment was assessed with disc diffusion test.Results The detection rate of virus was 35.4%(164/463)and that of enteric pathogenic bacteria was 41.6% (178/428)for the specimens.The major pathogens of viral diarrhea were NV and RV,with the detection rate of 14.9%(69/164)for NV and 8.2%(38/164)for RV.The main genotypes of RV were G3 (29.5%)and P8(24.1%).The detected pathogenic bacteria included mainly Shigella,Vibrio parahaemolyticus,and Salmonella.The main isolated Shigella strains were Shigella sonnei and Shigella flexneri and the major types of the Shigella toxin were type I and II enterotoxin (53.5%).The drug resistance rate of the Shigella strains was up to 94.8% to sulfamethoxazole Co,58.6% to ampicillin,and 34.5% to norfloxacin;the drug resistance rates of Shigella sonnei to the three antibiotics were much higher (100%,87.1%,and 61.3%)and the multi-drug resistance of the isolated Shigella sonnei strains was common.Conclusion The pathogenic spectrum of infectious diarrhea in Tianjin is complex and the drug resistance of isolated Shigella strains is common.