Abstract
Aim: The aim of this study was to assess the discriminatory power and potential turn around time (TAT) of a PCR‐based method for the detection of methicillin‐resistant Staphylococcus aureus (MRSA) from screening swabs.
Methods: Screening swabs were examined using the current laboratory protocol of direct culture on mannitol salt agar supplemented with oxacillin (MSAO‐direct). The PCR method involved pre‐incubation in broth for 4 hours followed by a multiplex PCR with primers directed to mecA and nuc genes of MRSA. The reference standard was determined by pre‐incubation in broth for 4 hours followed by culture on MSAO (MSAO‐broth).
Results: A total of 256 swabs was analysed. The rates of detection of MRSA using MSAO‐direct, MSAO‐broth and PCR were 10.2, 13.3 and 10.2%, respectively. For PCR, the sensitivity, specificity, positive predictive value and negative predictive values were 66.7% (95%CI 51.9–83.3%), 98.6% (95%CI 97.1–100%), 84.6% (95%CI 76.2–100%) and 95.2% (95%CI 92.4–98.0%), respectively, and these results were almost identical to those obtained from MSAO‐direct. The agreement between MSAO‐direct and PCR was 61.5% (95%CI 42.8–80.2%) for positive results, 95.6% (95%CI 93.0–98.2%) for negative results and overall was 92.2% (95%CI 88.9–95.5%).
Conclusions: (1) The discriminatory power of PCR and MSAO‐direct is similar but the level of agreement, especially for true positive results, is low. (2) The potential TAT for the PCR method provides a marked advantage over conventional methods. (3) Further modifications to the PCR method such as increased broth incubation time, use of selective broth and adaptation to real‐time PCR may lead to improvement in sensitivity and TAT.