Rapid detection of methicillin-resistant Staphylococcus aureus in screening samples by relative quantification between the mecA gene and the SA442 gene

Rapid detection of methicillin-resistant Staphylococcus aureus (MRSA) is important to identify patients colonized with this pathogen and implement infection control precautions. We aimed to improve the combined use of the mecA gene polymerase chain reaction (PCR) and the SA442 PCR to detect MRSA in clinical screening samples. In a true MRSA the mecA copy number will be equal to the SA442 copy number, whereas in samples with a methicillin-sensitive Staphylococcus aureus (MSSA) combined with a methicillin-resistant coagulase-negative Staphylococcus (MRCNS) the copy numbers will usually differ. Here we introduce a PCR system, relative quantification PCR (RQ-PCR), which takes this difference into account. RQ-PCR identifies true MRSA in clinical samples with a specificity that is comparable to the SCCmec-based PCRs.

► A mecA and S. aureus-specific (SA442) PCR can be combined to screen for MRSA.
► We aimed to improve the SA442/mecA PCR to identify MRSA in screening samples.
► Relative quantification (RQ) of SA442/mecA PCR detects MRSA with high sensitivity.
► Specificity is comparable to other SCCmec-based PCR tests.
► RQ-PCR will also detect exceptional SCCmec types, i.e., of veterinary origin.