MRSA Typing

We are introducing a new test for typing Methicillin Resistant Staphylococcus aureus (MRSA) strains. This test is based on a widely used method called 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.

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