Species and Serovar-Distribution, and Drug-Resistance of Shigella Strains Isolated from Imported and Domestic Cases during 1995-1999 in Tokyo

A total of 290 Shigella strains consisting of 180 imported strains and 110 domestic strains isolated during 1995-1999 in Tokyo were examined regarding their species and serovar-distribution and their drug-resistance. In both groups, S. sonnei (70.0% in the imported strains, 80.9% in the domestic strains) was found to be the most prevalent species, followed by S. flexneri (20.0% in the imported strains, 19.1% in the domestic strains). S. dysenteriae and S. boydii were only isolated in the imported cases. Among the S. flexneri serovar, 1b, 2a, 6, 2b, and 3a were predominant in the imported strains, whereas 1b and 2a were predominant in the domestic strains. Provisional new serovar Shigella strains were isolated from 11 imported cases and 2 domestic cases. The drug-resistance test using 9 drugs (CP, TC, SM, KM, ABPC, ST, NA, FOM, and NFLX) showed that 92.2% of the imported strains and 94.5% of the domestic strains were resistant to some of the drugs tested. Drug-resistance patterns of the resistant strains varied in 25 types. Among those, a triple drug-resistance type with TC.SM.ST was found as the most frequent pattern in both groups. None of the strains were resistant to NFLX.