Patent ID: 8187812

Claim:
A method for determining the presence or absence of methicillin-resistant Staphylococcus aureus in a sample, the method comprising, determining the presence or absence of an SCCmec insertion polynucleotide at an attB junction site within an orfX sequence of the Staphylococcus aureus DNA in the sample, wherein the orfX sequence, when the SCCmec insertion polynucleotide is absent, comprises a first target sequence on one side of the attB junction site and a second target sequence on the other side of the attB junction site, wherein the first and second target sequences are contiguous, said determining step comprising: contacting the sample with a first primer, a second primer, a blocker polynucleotide, a polymerase, and one or more nucleotide triphosphates, and exposing the sample to amplification conditions, wherein: (i) the first primer hybridizes to a first region of the first target sequence independent of the presence of the SCCmec insertion polynucleotide, the first region being proximal to the attB junction site, (ii) the second primer hybridizes to a second region of the first target sequence, the second region being distal to the first region relative to the attB junction site, wherein the second primer is capable of priming synthesis of a portion of the first target sequence spanned by the first and second regions of the first target sequence, and (iii) the blocker polynucleotide hybridizes to both contiguous first and second target sequences when the SCCmec insertion polynucleotide is absent, such that when the SCCmec insertion polynucleotide is present at the attB junction site, the first and second primers support exponential amplification of the portion of the first target sequence spanned by the first and second regions of the first target sequence, and when the SCCmec insertion polynucleotide is absent from the attB junction site, the blocker polynucleotide hybridizes to the contiguous first and second target sequences to block hybridization of the first primer to the first region of the first target sequence, so that amplification of the portion of the first target sequence spanned by the first and second regions of the first target sequence is inhibited, whereby the presence or absence of an amplified portion of the first target sequence is indicative of the presence or absence of methicillin-resistant Staphylococcus aureus in the sample.