A novel staphylococcal cassette chromosome mec (SCCmec) composite island (SCCmec AI16 -SCCczr AI16 -CI) was identified in Staphylococcus pseudintermedius. Four integration site sequences for SCC subdivided the 60,734-bp island into 41,232-bp SCCmec AI16 , 19,400-bp SCCczr AI16 , and 102-bp SCC-like AI16 elements. SCCmec AI16 represents a new combination of ccrA1B3 genes with a class A mec complex. SCCczr AI16 contains ccrA1B6 and genes related to restriction modification and heavy metal resistance. SCCmec AI16 -SCCczr AI16 -CI was found in methicillin-resistant S. pseudintermedius sequence type 112 (ST112) and ST111 isolated from dogs and veterinarians in Thailand.
Methicillin-resistant Staphylococcus pseudintermedius (MRSP) has been associated with clinical manifestations in companion animals and occasionally causes diseases in humans (1, 2). MRSP contains the staphylococcal cassette chromosome mec (SCCmec) element, which is defined by the presence of the mec gene that mediates -lactam resistance and by the cassette chromosome recombinase (ccr) gene(s) responsible for site-specific integration/excision of the element (3). Composite SCC structures containing two ccr gene complexes likely resulting from multiple element integrations have been increasingly reported in Staphylococcus aureus and in coagulase-negative staphylococci where such structures frequently carry heavy metal resistance gene clusters (3-9). So far, only five SCCmec elements have been completely characterized in MRSP, including SCCmec II-III, SCCmec VII-241, SCCmec V, ⌿SCCmec 57395 , and SCCmec IV, and are mainly associated with predominant clones of the following sequence types (ST): ST71, ST93, ST68, ST233, ST45,. Recently, MRSP strains of ST112 and ST111 (a single locus variant of ST112) isolated from dogs and veterinarians in Thailand were found to contain an unusual combination of the class A mec gene complex with the type I ccr gene complex, suggesting a new SCCmec type (15). We therefore aimed to characterize this novel SCCmec element and to determine whether it is conserved within other MRSP isolates of the same clonal lineage.Identification of the SCCmec AI16 -SCCczr AI16 composite element (CI). MRSP strains of ST111 and ST112 were obtained from a previous study and are listed in Table 1 (15). Phenotypic and genotypic characteristics, including those determined by antimicrobial susceptibility testing and antibiotic resistance gene detection, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST), were determined previously (15). In this study, the strains were additionally tested for mec-associated direct repeat unit (dru) and spa types (16, 17), for the presence of the novel SCCmec element, and for resistance to heavy metals. The genomic DNA of all strains was extracted using the peqGOLD bacterial DNA kit (Peqlab Biotechnologie GmBH, Jena, Germany), and that of strain AI16 was sequenced using Ion Torrent semiconductor (Life Technologies, Carlsbad, CA) and Illumina MiSeq (Illumina, San Diego, CA) technologies. S...