MRSA SCCmec epidemiology in Israel: development and implementation of an MRSA SCCmec typing strategy

Staphylococcal cassette chromosome mec (SCCmec) typing is essential for investigating the molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA). Published assays were often found to be limited in their ability to characterize isolates that were not collected locally. We aimed to develop, test, and implement a molecular method which would enable the SCCmec classification of a large collection of MRSA isolates in a routine clinical laboratory. A multistep working algorithm consisting of two main steps and four additional supplementary steps was developed, using previously reported primers. A total of 1,008 isolates obtained locally, by both clinical and screening cultures, were tested. The majority of isolates (82.54%) could be classified using two main reactions. Overall, our MRSA SCCmec typing strategy was able to classify 917/1,008 (90.97%) of the MRSA isolates. The most predominant was type II SCCmec (41%); a high prevalence of type V SCCmec (16.37%) was also found. PVL gene carriage was found among two type IV SCCmec isolates only. We present a logistically feasible, multistep, MRSA SCCmec typing algorithm which can be used to type a large collection of MRSA isolates. The distinctly higher prevalence of SCCmec type V might reflect a unique MRSA distribution pattern in Israel.