The strain collection consisted of MRSA from various clinical sources (e.g., blood cultures and wound infections) and included surveillance cultures from patients and staff. Of all clinical S. aureus isolates, 6.4% exhibited methicillin resistance in 2003. For species identification, every strain was tested with API ID 32 Staph (bioMérieux, Marci l'Etoile, France) and for the presence of free coagulase. The presence of the mecA gene responsible for methicillin resistance was confirmed using PCR [18 (link)]. The sequence of the short sequence repeat region of the spa gene encoding the S. aureus protein A was determined in 557 strains [14 (link)]. The primers spa-1113f (5′- TAA AGA CGA TCC TTC GGT GAG C −3′) and spa-1514r (5′- CAG CAG TAG TGC CGT TTG CT −3′) were used for spa amplification and Taq Cycle sequencing. DNA sequences were obtained with an ABI Prism 3100 Avant Genetic Analyzer (Applied Biosystems, Foster City, California, United States) and analyzed with the Ridom StaphType software version 1.5 beta (Ridom GmbH, Würzburg, Germany) incorporating the newly added automated early warning system (“clonal alerts”) for MRSA cluster detection [14 (link)]. Typability, discriminatory index, and the 95% confidence interval (CI) of the discriminatory index were calculated using the procedures published previously [19 (link),20 (link)].
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