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用聚合酶链反应（ＰＣＲ）检测伤寒患者血液标本中伤寒杆菌。根据伤寒杆菌鞭毛抗原基因ＤＮＡ的核苷酸序列，合成２对寡核苷酸引物，以该基因的ＤＮＡ片段作为模板，经首次ＰＣＲ和巢式ＰＣＲ扩增后。产物分别为４５８ｂｐ和３４３ｂｐ的寡核苷酸片段。首次ＰＣＲ检测的敏感度可达１０条伤寒杆菌ＤＮＡ水平。对１０例有伤寒临床表现、血培养有伤寒杆菌生长的患者的血液标本进行了ＰＣＲ检测，结果，首次ＰＣＲ检测９例呈阳性；嵌套式ＰＣＲ检测１０例均呈阳性。对其中３例伤寒患者的血清和白细胞分别作ＰＣＲ检测，结果均呈阳性。这些结果提示大部分伤寒患者的血清标本只需作首次ＰＣＲ检测即可呈阳性。由于作者对标本的预处理方法作了改进，于９ｈ后可获首次ＰＣＲ结果
Salmonella typhi in blood samples of patients with typhoid fever were detected by polymerase chain reaction (PCR). Two pairs of oligonucleotide primers were synthesized based on the nucleotide sequence of the DNA of Salmonella typhi flagella antigen and amplified by the first PCR and nested PCR using the DNA fragment of the gene as a template. The products were 458 bp and 343 bp oligonucleotide fragments, respectively. The sensitivity of the first PCR assay can reach 10 Salmonella typhi DNA levels. Ten cases of patients with clinical manifestations of typhoid and blood cultures of patients with Salmonella typhi were detected by PCR. Nine of them were positive by first PCR, and 10 by nested PCR. Three cases of typhoid fever in patients with serum and leucocyte were detected by PCR, the results were positive. These results suggest that serum samples from most patients with typhoid fever are only positive for the first PCR test. The first PCR results were obtained after 9 h as the authors made improvements to the specimen pretreatment