MRSA Typing

MRSA typing is intended to be used for outbreak investigations where MRSA isolates are compared pair-wise for the degree of relatedness*.

This test is based on a widely used method called the spa-typing, which compares the length and sequence of a specific repeated DNA element within the protein A gene (spa) from MRSA isolates. This basic spa-typing method was further improved by extending the comparison of length of the repeated sequence elements to 6 other genes within the genome of MRSA. Inclusion of these additional loci that exhibit variable number tandem repeats (VNTR) increased the discriminatory power of the typing method. Unrelated strains of MRSA show a higher degree of difference in sequence and/or length of these VNTR elements than identical and closely related strains. This combined method (spa & VNTR) for MRSA typing has a discriminatory power similar to that of Pulsed Field Gel Electrophoresis (PFGE), but a shorter waiting period for typing results.

*If you want to type a single MRSA isolate, we will only determine the spa-type of the isolate based on the repeat code published by Shopsin et al. (1999) Journal of Clinical Microbiology Vol. 37, No 11, 3556-3563. This spa-type can be then compared with other MRSA strains whose spa-types are known.