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This study was conducted to investigate the distribution of rotavirus genotypes in Nara Prefecture, Japan before and after the introduction of rotavirus vaccination in 2011. Since the 2011/2012 season, DS-1-like G1P[8] strains have been detected in Nara Prefecture, accounting for about half of all strains in the 2014/2015 season. During the 2015/2016 season, no DS-1-like G1P[8] strains were detected; G2P[4] was the predominant genotype.

We conducted a survey of diarrhea stool samples in which no virulent agents had previously been detected at clinical laboratories. DNA extracted directly and purified from the diarrhea stool was tested for bacterial pathogenic genes by polymerase chain reaction. The test results for 85 specimens were as follows: one sample was positive for lt, ipaH, and eae; two were positive for aggR; and eight were positive for astA. Inoculation with the stool specimens led to the isolation of a strain of Escherichia coli possessing eae, three strains of E. coli possessing astA, and a strain of Klebsiella possessing astA.