Background: Salmonella enterica serovars often have a broad host range and cause some gastrointestinal and systemic diseases. The diagnosis of typhoid fever or paratyphoid fever is made by ordinary culture methods and biochemical tests. However, a more rapid and alternative method of diagnosing these diseases is in need since the classical diagnostic method requires several days for a result. Some researchers have already reported serovar Typhi detection methods with PCR using the fliC-d gene and the Vi capsular antigen gene.

Methods: Thirty-six Salmonella strains isolated at Pusan National University Hospital from 1997 to 2004 were used for a rapid identification of S. enterica serovars Typhi and Paratyphi A with multiplex PCR that uses the O (rfbE, rfbS), H (fliC-d, fliC-a), and Vi (viaB) antigen genes. To further characterize these Salmonella strains, we used PCR to detect genes (invA and enterotoxin) for proposed virulence factors and performed antimicrobial susceptibility testing, serotyping and pulsed-field gel electrophoresis for epidemiological characteristics.

Results: Most strains were resistant to ampicillin. By PCR, tyv, prt, fliC-d and viaB genes were detected in serovar Typhi, whereas only fliC-a and prt genes were found in serovar Paratyphi A. In addition, invA and enterotoxin genes were detected in both strains.

Conclusion: This method enabled us to identify and differentiate serovars Typhi and Paratyphi A by only a single PCR assay. That is, clinically important human pathogens were more rapidly and specifically detected and identified with multiplex PCR. (Korean J Clin Microbiol 2007;10:6-13)