Identification of Nocardia species based on secA1 gene

Objective To evaluate the role of secA1 gene for identifying and typing Nocardia species. Methods secA1 gene sequences of 59 Nocardia strains were amplified by polymerase chain reaction (PCR) and purified products were sequenced and then used for similarity analysis of secA1 by using DNAStar software, meanwhile the secA1 gene sequences of another 32 Nocardia strains were downloaded from GenBank. The phylogenetic tree based on secA1 gene was constructed by using Mega 6.06 software (neighbor-joining method). Results The intra and inter species similarity of 91 strains of Nocardia was 97.2% to 100.0% and 85.2% to 98.4% respectively (averagely 98.6% and 91.8% respectively). In the phylogenetic tree based on secA1 gene sequences, the 16 Nocardia species were accurately divided into 16 different clusters, especially the close species, including Nocardia complex. Conclusion Sequencing of secA1 is a novel method for identifying and typing Nocardia species, especially for the close species.