DETECTION AND IDENTIFICATION OF LEPTOSPIRA-INTERROGANS SEROVARS BY PCR COUPLED WITH RESTRICTION-ENDONUCLEASE ANALYSIS OF AMPLIFIED DNA

Primers for PCR were selected from a sequenced fragment of clone pL590, which contains a repetitive element present in the genome of Leptospira interrogans serovar hardjo type hardjoprajitno (M. L. Pacciarini, M. L. Savio, s. Tagliabue, and C. Rossi, J. Clin. Microbiol. 30:1243-1249, 1992). A specific DNA fragment was amplified from the genomic DNAs of serovar hardjo type hardjoprajitno and nine serovars also belonging to L. interrogans is a consequence of the spread of the same or a closely related repetitive element within this species (Pacciarini et al., J. Clin. Microbiol. 30:1243-1249, 1992). In addition, specific amplification was obtained from two Leptospira borgpetersenii serovars (tarassovi and hardjo type hardjobovis). Negative PCR results were observed with all of the other Leptospira serovars tested, including nonpathogenic ones (serovars patoc and andamana), another spirochete (Borrelia burgdorferi), bacteria commonly found in biological samples, and swine and bovine cell lines. Direct PCR on biological samples such as kidney samples demonstrated that preliminary isolation and culture of Leptospira cells are not required for efficient detection. Furthermore, digestion of the amplified DNA with the enzymes HinfI and DdeI yielded specific polymorphic patterns, allowing discrimination among the majority of the serovars. These methods were applied to 25 field isolates of serovar pomona, leading to the conclusion that they were suitable for the simple and rapid detection of L. interrogans and for serovar identification.