[Establishment and application of a multilocus sequence typing assay for Corynebacterium striatum]

Objective: To establish a multilocus sequence typing (MLST) assay for Corynebacterium (C.) striatum, explore the population structure and evolution relationship of clinical isolates of C. striatum. Methods: Seven housekeeping genes (gyrA, gyrB, hsp65, sodA, secA1, rpoB, 16S rRNA) were amplified with PCR by using self-designed specific primers and sequenced. Then, the sequences were assembled with software SeqMan. The gene diversity and gene recombination characteristics were evaluated by using software DnaSP 5.10.01 and Splits tree 4.14.2. The phylogenetic tree and the minimum spanning tree were constructed based on the sequence types (ST) characteristics by using software MEGA 7.0.14 and BioNumerics, respectively. In addition, the genetic evolutionary relationship among STs were analyzed by using software eBURST 3.0. Results: The expected amplification products of seven sites selected in all the test strains were obtained. Splits tree showed that the clustering of all C. striatum strains was consistent, suggesting that gene recombination is the potential driving force for the evolution of C. striatum. All of the 344 C.striatum strains were divided into 72 STs by MLST and 85.7% of the strains formed clonal complexes. CC19 was the predominant clonal complex, whereas ST16 in the clonal complex was detected in the most strains. ST had a certain geographic clustering and a certain correlation with the isolation time. Conclusions: C. striatum showed high genetic diversity in China and CC19 was the predominant clonal complex. The MLST assay established in this study can be used for the typing of C. striatum, but further improvement is needed.