[Detection of the microquantity DNA of Leptospira interrogans by polymerase chain reaction].

Leptospirosis is a severe zoonosis in the world. The methods for detecting leptospira are not sensitive and specific so far. The problems in early diagnosis and epidemiological identification of Leptospirosis remain unsolved. Two recombinant DNA fragments of serogroup Icterohaemorrhagiae, Leptospira were selected by repeated molecular cloning and screening in this study firstly. One of them can hybridize with the DNA of various serogroups of Leptospira interrogans; the other can only hybridize with the DNA of serogroup Icterohaemorrhagiae. After the nucleotides sequence analysis, from these 2 recombinant DNA fragments, 2 pairs of polymerase chain reaction (PCR) oligonucleotide primers were synthesized, named primer B 1, 2 and primer B 3, 4 PCRs were carried out with these 2 primers for detecting the microquantity (0.1 ng) of various serovars, serogroup of leptospires. All the DNA of Leptospira interrogans can be amplified by primer B 1, 2, and only the DNA of serogroup icterohaemorrhagiae, Leptospira reacted specially with primer B 3, 4. The DNA of non-pathogenetic Leptospira and some other microbes, however, had no amplification at all. This study is first reported at home and abroad. The results demonstrate that PCR is a very sensitive and specific technique of DNA amplification, which can be used as a powerful tool in the early diagnosis and epidemiological identification of leptospirosis.