Prevalence and genetic properties of Salmonella enterica serovar typhimurium definitive phage type 104 isolated from Rattus norvegicus and Rattus rattus house rats in Yokohama City, Japan.

Salmonella enterica serovar Typhimurium was isolated from the intestinal contents of Rattus rattus and Rattus norvegicus house rats captured at two buildings, designated buildings J and YS, in Yokohama City, Japan. From October 1997 to September 1998, 52 of 339 (15.3%) house rats were found to carry Salmonella serovar Typhimurium definitive phage type 104 (DT104). In building J, 26 of 161 (16.1%) house rats carried DT104 over the 1-year study period, compared to 26 of 178 (14.6%) rats in building YS. The isolation rates of DT104 from R. rattus and R. norvegicus were similar in the two buildings. Most DT104 strains from building J (24 of 26) showed resistance to ampicillin, chloramphenicol, streptomycin, sulfisoxazole, and tetracycline and contained both the 1.0- and 1.2-kbp integrons, carrying genes pse1, pasppflo-like, aadA2, sulI, and tet(G). All DT104 strains from building YS were resistant to ampicillin and sulfisoxazole, and had the 1.2-kbp integron carrying pse1 and sulI. Cluster analysis of pulsed-field gel electrophoresis patterns of BlnI-digested DT104 DNAs showed that 22 of 26 DT104 strains from building J and 24 of 26 strains from building YS could be grouped into separate clusters each specific for the building origin. These results indicated that DT104 strains were prevalent in house rat colonies in each building and suggest that house rats may play an important role in the epidemiology of DT104.

An improved enrichment broth for isolation of Escherichia coli O157, with specific reference to starved cells, from radish sprouts.

An enrichment broth was developed for the efficient isolation of Escherichia coli O157 from radish sprouts. The broth was buffered peptone water containing 0.5% sodium thioglycolate (STG-BPW), which was designed to allow growth of E. coli O157 in starved and unstarved states. However, this medium suppressed the growth of non-carbohydrate-fermenting obligate aerobes whose colonial appearance on sorbitol MacConkey agar containing cefixime and tellurite (CT-SMAC) resembled that of E. coli O157. Both starved and unstarved cells of E. coli O157 experimentally inoculated into radish sprouts were successfully recovered with STG-BPW enrichment in all cases, most of which showed marked disappearance of E. coli O157-like colonies on CT-SMAC.

[Shigella boydii strains possessing a new serovar (SM00-27) isolated from diarrhea of overseas travelers in Japan].

Five Shigella strains isolated from stool cultures of five sporadic imported diarrheal cases in Japan during 1999-2001, did not react to any antisera of the established Shigella serovars. These strains had the typical biochemical characteristics of Shigella boydii, and were biochemically identical. All strains were positive in a PCR assay and a cultured-cell invasion test for invasiveness; these indicate that they can cause shigellosis in humans. The results of antigenic analysis revealed that they did not belong to any of the recognized or provisional serovars, and were serologically indistinguishable. Strain SM00-27 is designated as the test strain for this new S. boydii serovar.

Evaluation of sorbitol-salicin MacConkey medium containing cefixime and tellurite (CT-SSMAC medium) for isolation of Escherichia coli O157:H7 from raw vegetables.

The utility of CT-SSMAC medium (sorbitol-salicin MacConkey medium containing cefixime and tellurite) for the isolation of Escherichia coli O157:H7 from raw vegetables was investigated. The colonies of all E. coli O157:H7 and O157:NM strains tested were colorless and beta-galactosidase-positive on CT-SSMAC medium. Furthermore, the number of colorless colonies on the CT-SSMAC medium was less than that on the sorbitol MacConkey medium containing cefixime and tellurite (CT-SMAC medium) from several raw vegetable samples. All colorless colonies grown on CT-SSMAC medium from raw vegetable samples were beta-galactosidase-negative. These findings suggest that the CT-SSMAC medium is useful for the isolation of E. coli O157:H7 from raw vegetable samples.