Détection de la colonisation nasale de Staphylococcus aureus résistant à la méthicilline : étude prospective comparant l'amplification génique temps réel vs les milieux chromogènes sélectifs Detection of nasal colonization methicillin-resistant Staphylococcus aureus: a prospective study comparing real-time genic amplification assay vs selective chromogenic media

In contrast to « classical » genic amplification, real-time genic amplification can be performed in every laboratory without the need of sophisticated isolation procedures. Moreover, real-time genic amplification allows an early detection of meticillin resistant Staphylococcus aureus colonization, 2 hours compared to 1 or 2 days for culture. Objective. – In order to assess the feasibility on Smartcycler of the IDI-MRSATM real-time genic amplification assay in comparison with chromogenic media. Methods. – A prospective study has been initiated in July 2004: nasal swabs were taken from patients entering the ICU, vascular surgery, diabetology and geriatry wards. During a 4 months period, 682 specimens have been obtained from 508 patients. Results. – Sixty-four (9.3%) patients were positive by genic amplification and selective agar culture (CHROMagar MRSA, MRSASelect and/or ORSAB), 19 (2.9%) were positive by genic amplification only (3 of these patients were under antibiotic treatment); 572 specimens remained negative by both methods. The sensitivity and specificity of this assay were 100% and 96% respectively with a positive predictive value of 70% and negative predictive value of 100%. Initially 82 nasal specimens were unresolved (12%). 38 were resolved following a freezethaw cycle. Thus, 44 (6.4%) were unresolved specimens. Comparison between CHROMagar MRSA and MRSASelect showed a good correlation for the detection at 24 hours (5.5% and 5.6% respectively). These two chromogenic media allowed a much better detection of MRSA than ORSAB medium within 24H. Conclusion. – The results obtained by the early real-time genic amplification for the detection of meticillin resistant Staphylococcus aureus are promising. Despite 6.4% amplification failure, we consider that IDI-MRSATM real-time genic amplification assay represents a significant breakthrough in the detection of colonization. © 2006 Elsevier SAS. Tous droits reserves. Mots cles : PCR temps reel ; Staphylococcus aureus ; Resistance a la methicilline ; Detection nasale