Multiplex-PCR method for species identification of coagulase-positive staphylococci

Abstract

In veterinary medicine, coagulase-positive staphylococci (CoPS) other than Staphylococcus aureus have frequently been misidentified as being S. aureus strains, as they have several phenotypic traits in common. There has been no reliable method to distinguish among CoPS species in veterinary clinical laboratories. In the present study, we sequenced the thermonuclease (nuc) genes of staphylococcal species and devised a multiplex-PCR (M-PCR) method for species identification of CoPS by targeting the nuc gene locus. To evaluate sensitivity and specificity, we used this M-PCR method on 374 staphylococcal strains that had been previously identified to the species level by an hsp60 sequencing approach. We could successfully distinguish between S. aureus, S. hyicus, S. schleiferi, S. intermedius, S. pseudintermedius, and S. delphini groups A and B. The present method was both sensitive (99.8%) and specific (100%). Our M-PCR assay will allow the routine species identification of CoPS isolates from various animal species for clinical veterinary diagnosis.

FIG. 1.

Phylogenetic tree based on complete thermonuclease (nuc) gene sequences in staphylococci. The tree was constructed by the neighbor-joining method using CLUSTAL W.

FIG. 2.

Electrophoresis after multiplex PCR for species identification of coagulase-positive staphylococci (CoPS) on a 1.0% agarose gel. Lanes: 1, S. aureus; 2, S. intermedius; 3, S. schleiferi; 4, S. delphini group A; 5, S. hyicus; 6, S. pseudintermedius; 7, S. delphini group B; 8, S. lutrae; 9, S. felis; 10, water (negative control).