Evaluation of the lightcycler methicillin-resistant Staphylococcus aureus (MRSA) advanced test for detection of MRSA nasal colonization

W. C. Yam, Kit Hang Siu, P. L. Ho, T. K. Ng, T. L. Que, K. T. Yip, Cathie P.K. Fok, Jonathan H.K. Chen, Vincent C.C. Cheng, K. Y. Yuen

Research output: Journal article publicationJournal articleAcademic researchpeer-review

20 Citations (Scopus)


Rapid detection of methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization is crucial for the prevention and control of MRSA infections in health care settings. The LightCycler MRSA Advanced Test (Roche Diagnostics) is a commercially available real-time PCR assay for direct detection of MRSA nasal colonization by targeting of the staphylococcal cassette chromosome mec (SCCmec)-orfX junction. The diagnostic performance of the assay was compared with that of ChromID MRSA agar (bioMérieux) culture and an in-house duplex real-time PCR assay. Among 1,246 nasal swab specimens collected from 2 general hospitals in Hong Kong, 174 (14%) were considered true positive for MRSA. Chromogenic culture and the in-house real-time PCR assay identified 147 (84.5%) and 133 (76.4%) true-positive cases with specificities of 100% and 98.6%, respectively. Based on the target melting temperature (Tm) values (57.0 to 62.0°C) defined by the manufacturer, the LightCycler MRSA Advanced Test identified only 85 (48.9%) true-positive specimens. Interestingly, an additional 60 (34.5%) true-positive specimens were detected despite atypical Tm values of 55°C, providing overall sensitivity and specificity values of 83.3% and 99%, respectively. Among isolates with Tm values of 55°C, most were typed as clonal complex 45 (CC45). By sequence analysis of the SCCmec-orfX junction, characteristic single-nucleotide polymorphisms (SNPs) were identified only in isolates with Tm values of 55°C and not in those with typical Tm values. It is conceivable that those SNPs were located inside the target region of the proprietary hybridization probes, which resulted in a Tm shift in the melting curve analysis. Our study highlights the importance of a global evaluation of commercial kits so that the interpretation algorithm covers different lineages of MRSA clones prevalent in various geographical regions.
Original languageEnglish
Pages (from-to)2869-2874
Number of pages6
JournalJournal of Clinical Microbiology
Issue number9
Publication statusPublished - 1 Sept 2013
Externally publishedYes

ASJC Scopus subject areas

  • Microbiology (medical)


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