Background: In the year 1996, there were some outbreaks of Salmonella typhi infection in Pusan and therefore, the incidence of S. typhi infection was markedly increased in comparison with the previous year. To differentiate the isolates epidemiologically, a random amplified polymorphic DNA (RAPD) fingerprinting method has been developed.

Methods: A total of 9 arbitrary primers were screened with S. typhi strains isolated in Pusan, 1996. This allowed selection of a panel of primers capable of detecting DNA polymorphisms among S. typhi isolates. This panel was used to examine 54 strains of S. typhi, which had been isolated in Pusan including the cases of outbreaks that was previously characterized by phage typing.

Results: Four single primers and one combination of two primers were selected to discriminate the S. typhi isolates. RAPD analysis resolved the 54 strains into 20 different subtypes. At least two outbreaks were found by RAPD analysis. The isolates of E1 phage type, which are the most common in Korea, were perfectly differentiated with each other, except the strains isolated within the outbreaks.

Conclusion: The RAPD approach is the useful epidemiologic tool to S. typhi subtyping, which is providing high discriminatory power. There were at least two outbreaks when the epidemic Salmonella infections of Pusan in 1996 had been occurred. The primers or their combination capable to discriminate the S. typhi isolates were described. (Korean J Clin Microbiol 1998;1(1):51-56.)