Comparison of two PCR-based methods and conventional culture for the detection of nasal carriage of Staphylococcus aureus in pre-operative patients

Nasal carriage is an important risk factor for the development of post-operative infections with Staphylococcus aureus and pre-operative treatment with mupirocin in carriers reduces the post-operative infection rate. Therefore, it is important to identify nasal carriage rapidly. Two polymerase chain reaction (PCR) techniques were compared to conventional culture in surgical patients. In 404 consecutive patients, nasal swabs were taken for pre-operative screening for the nasal carriage of S. aureus. The performance of the Roche Staphylococcus Kit on Lightcycler (Roche; RSA) and the Becton Dickinson (San Diego, CA) GeneOhm StaphSR assay on Smartcycler (Cepheid; BDSA) were compared with semi-quantitative culture. The sensitivity for culture, RSA and BDSA compared to the gold standard was 98.2, 82.0 and 85.6%, respectively, and the specificity was 100, 98.3 and 99.3%, respectively. The lower sensitivity of both PCR techniques was associated with samples with low bacterial loads. The RSA and BDSA were similar in performance and are suitable for the pre-operative identification of nasal carriers of S. aureus.