Genome analysis of an SCCmec element in ST9-MRSA from Myanmar with a unique mec gene complex and two ccr gene complexes (ccrA1B1 and ccrA5B7).

Abstract

The staphylococcal cassette chromosome mec (SCCmec) is a mobile genetic element among staphylococcal species that confers β-lactam resistance to its host bacteria. SCCmec types, as well as their specific sequence types, play a critical role in epidemiological analyses of MRSA. An SCCmec element contains two essential components that determine its type: the mec gene complex (mecA/mecC gene and its flanking regions) and the cassette chromosome recombinase gene (ccr) complex. Fifteen SCCmec types (I–XV) are recognized by the International Working Group on the Classification of Staphylococcal Cassette Chromosome Elements (IWG-SCC), with different subtypes making up each one based on the nature of the joining (J) region.1,2 Our previous report of an ST9-MRSA-IX (strain S286) from an outpatient in Yangon was the first report of a type IX SCCmec from Myanmar.3 SCCmec type IX consists of the type 1 ccr gene complex and the class C2 mec gene complex (1C2), and it is predominantly detected in Thailand and Taiwan.4,5 ST9 is a frequent lineage among livestock-associated MRSA (LA-MRSA) in Asia, and epidemiological studies suggest the cross-species transmission of this lineage.6 The genomic structure of SCCmec IX was determined on the basis of only two MRSAs, ST398-MRSA JCSC6943 and ST9-MRSA JCSC6690, obtained from Thailand (Figure 1).7,8 In this study, the precise genomic features of the SCCmec in strain S286 (SCCmecS286) were determined. Its evolution and relationship to known SCC elements are discussed as well.