Comparison of complete rpoB gene sequence typing and multi-locus sequence typing for phylogenetic analysis of Staphylococcus aureus.

The present study determined the complete rpoB and seven partial house-keeping gene sequences of 29 human (20) and poultry (9) strains of Staphylococcus aureus, and conducted a phylogenetic analysis together with 39 strains in the GenBank and EMBL databases. On the basis of complete rpoB gene sequence (RS) typing, 28 different rpoB sequence types (RSTs) were identified; however, only 23 multilocus sequence types (STs) were identified by multi-locus sequence typing (MLST). RST 2-1 was a major RST covering 23.5% (16/68) of the analyzed strains followed by RST 4-1 (14.7%, 10/68). Out of 10 poultry strains including one in the database, 9 and 1 were classified into unique RSTs 3-1 and 6-3, respectively. According to the MLST, ST5 was a major sequence type covering 25.0% (17/68) of them, followed by STs 228 and 239 (for each ST, 11.8%, 8/68), and poultry strains were grouped into ST5 (9/10) and ST692 (1/10). The poultry ST5 strains were differentiated from human ST5 strains and rifampin resistance-related mutations were observed in some human S. aureus strains by RS typing. Thus, RS typing was more discriminative and informative than MLST, and it can be a simple and economic alternative to MLST for identification and phylogenetic analysis of S. aureus.