Detection of the H1-j strain of Salmonella typhi among Korean isolates by the polymerase chain reaction.

Salmonella typhi, the etiologic agent of typhoid fever, typically has only a phase-1 flagellar antigen, H1-d (fliC). While most strains of S. typhi have H1-d antigen, 10-20% of Indonesian isolates have been reported to possess H1-j antigen instead. To investigate the presence H1-j strains of S. typhi isolates in Korea, where typhoid fever is still a common infectious problem, we used the polymerase chain reaction (PCR) with a pair of oligonucleotides primers that specifically amplified the flagellin gene of S. typhi. Of 375 isolates of S. typhi tested, only one was shown to possess the H1-j antigen, which was shown by the presence of a 1,269-basepair fragment on agarose gel electrophoresis after the PCR. The isolate with the H1-j antigen was cultured from a Korean-Indonesian man who was already symptomatic in Indonesia and was thought to be an Indonesian strain. Because 375 strains tested in this study were collected from cases with typhoid fever in different regions of Korea during the period from 1986 to 1991, it could be concluded that the mutation rate to j antigen is negligible among S. typhi endemic in Korea.