SELECTIVE AMPLIFICATION OF ABEQUOSE AND PARATOSE SYNTHASE GENES (RFB)BY POLYMERASE CHAIN-REACTION FOR IDENTIFICATION OF SALMONELLA MAJOR SEROGROUP-A, SEROGROUP-B, SEROGROUP-C2, AND SEROGROUP-D

Many parts of the Salmonella rfb gene clusters which are responsible f or biosynthesis of the oligosaccharide-repeating units of the O-antige nic lipopolysaccharide have recently been cloned and sequenced. On the basis of this knowledge, three sets of nucleotide primers were select ed to target defined regions of the abequose and paratose synthase gen es: rfbJ of Salmonella serogroup B, rfbJ of Salmonella serogroup C2, a nd rfbS of Salmonella serogroup D (also present in serogroup A). For g ood differentiation among these major serogroups, the primers were des igned not only to give precise specificity in priming but also to give DNA products with different sizes in polymerase chain reactions (prod uct sizes, approximately 720 bp for both serogroups A and D, approxima tely 820 bp for serogroup C2, and approximately 882 bp for serogroup B ). In a polymerase chain reaction assay utilizing these rfb-specific p rimers, all of the 40 salmonellae belonging to serogroups B, C2, and D plus A were accurately identified among a total of 123 clinical isola tes tested (including 55 salmonellae from 36 different serotypes and 6 8 strains from 10 other members of the family Enterobacteriaceae). No false-positive reactions were detected. The selected rjb gene sequence s were proved for the first time to be useful DNA-based markers for id entification of and differentiation among Salmonella serogroups A, B, C2, and D.