Sumio Yamada

A sensitive method for the detection of enterotoxigenic Escherichia coli by the polymerase chain reaction using multiple primer pairs.

In this study, a polymerase chain reaction (PCR) method has been developed for the detection of enterotoxigenic Escherichia coli (ETEC). Three different sets of oligonucleotide primers synthesized were used to amplify the enterotoxin genes of heat-labile (LTh) and heat-stable (STIa and STIb) enterotoxins of ETEC. These primers amplified a 627, 240, or 169 base pair (bp) DNA fragment from LTh, STIa and STIb gene, respectively, of the reference ETEC strains. The addition of RNase A (10 micrograms/ml) to the PCR reaction solution diminished nonspecific amplification of DNA fragments other than the enterotoxin genes. Five types of ETEC strains corresponding to the LTh, STIa, STIb, LTh-STIa, or LTh-STIb genotypes were distinguished by a single procedure of PCR using the mixture of the three sets of primers. PCR, hybridization, and conventional methods were subjected to one hundred stool specimens from diarrheal patients. It was found that PCR was the most sensitive method among them. These results suggested that PCR with triple primer pairs would be useful for the laboratory diagnosis of ETEC in the stool specimens.

Vibrio fluvialis andV. furnissii serotyping scheme for international use

A combination of two serotyping systems forVibrio fluvialis andV. furnissii, which were developed independently at the National Institute of Health (Tokyo) and Tokyo Metropolitan Research Laboratory of Public Health (Tokyo), was established as a single serotyping scheme comprising 35 O-antigen groups for international use.

Shigella dysenteriae strains having a provisional serovar isolated from imported diarrheal cases in Tokyo

Two bacterial strains (ME448 and ME474) isolated from stool cultures of imported cases in Tokyo in 1987 had typical biochemical characteristics of Shigella dysenteriae. The results of antigenic analyses showed that they were serologically identical to each other, but did not belong to any of the established Shigella serovars. These strains were positive for Serény test in guinea pig eye and cell-invasion test in HeLa cells. The strains also had virulence-plasmid encoding outer membrane proteins, indicating that they were pathogenic. We then contacted the Centers for Disease Control in the United States and the Central Public Health Laboratory in the United Kingdom and arranged serological examinations of the strain ME448. From the results, the strain was confirmed to have provisional S. dysenteriae serovar E23507. Although the serovar had been isolated from a Swedish patient who developed diarrhea while in India, this is thought to be the first report of its isolation in Japan.