Conville Patricia S, Zelazny Adrian M, Witebsky Frank G
Microbiology Service, Department of Laboratory Medicine, Warren G. Magnuson Clinical Center, National Institutes of Health, U.S. Department of Health and Human Services, 10 Center Drive, MSC 1508, Bethesda, MD 20892-1508, USA.
J Clin Microbiol. 2006 Aug;44(8):2760-6. doi: 10.1128/JCM.00155-06.
Molecular methodologies, especially 16S rRNA gene sequence analysis, have allowed the recognition of many new species of Nocardia and to date have been the most precise methods for identifying isolates reliably to the species level. We describe here a novel method for identifying Nocardia isolates by using sequence analysis of a portion of the secA1 gene. A region of the secA1 gene of 30 type or reference strains of Nocardia species was amplified using secA1-specific primers. Sequence analysis of 468 bp allowed clear differentiation of all species, with a range of interspecies similarity of 85.0% to 98.7%. Corresponding 16S rRNA gene sequences of a 1,285-bp region for the same isolates showed a range of interspecies similarity of 94.4 to 99.8%. In addition to the type and reference strains, a 468-bp fragment of the secA1 gene was sequenced from 40 clinical isolates of 12 Nocardia species previously identified by 16S rRNA gene sequence analysis. The secA1 gene sequences of most isolates showed >99.0% similarity to the secA1 sequences of the type or reference strain to which their identification corresponded, with a range of 95.3 to 100%. Comparison of the deduced 156 amino acid sequences of the SecA1 proteins of the clinical isolates showed between zero and two amino acid residue differences compared to that of the corresponding type or reference strain. Sequencing of the secA1 gene, and using deduced amino acid sequences of the SecA1 protein, may provide a more discriminative and precise method for the identification of Nocardia isolates than 16S rRNA gene sequencing.
分子方法，尤其是16S rRNA基因序列分析，已使许多新的诺卡菌属物种得以识别，并且迄今为止一直是在种水平上可靠鉴定分离株的最精确方法。我们在此描述一种通过对secA1基因的一部分进行序列分析来鉴定诺卡菌分离株的新方法。使用secA1特异性引物扩增了30株诺卡菌属物种的类型菌株或参考菌株的secA1基因区域。对468 bp的序列分析能够清晰地区分所有物种，种间相似性范围为85.0%至98.7%。相同分离株的1285 bp区域的相应16S rRNA基因序列显示种间相似性范围为94.4%至99.8%。除了类型菌株和参考菌株外，还对先前通过16S rRNA基因序列分析鉴定的12种诺卡菌属物种的40株临床分离株的secA1基因的468 bp片段进行了测序。大多数分离株的secA1基因序列与它们鉴定所对应的类型菌株或参考菌株的secA1序列显示出>99.0%的相似性，范围为95.3%至100%。临床分离株的SecA1蛋白推导的156个氨基酸序列与相应的类型菌株或参考菌株相比，氨基酸残基差异为零至两个。与16S rRNA基因测序相比，secA1基因测序以及使用SecA1蛋白的推导氨基酸序列可能为诺卡菌分离株的鉴定提供一种更具区分性和精确性的方法。
