A new SCCmec element in a Staphylococcus cohnii clinical isolate might be an ancestral structure of type III SCCmec
Abstract number: P957
Objective: To characterize a "non-typeable" SCCmec in a Staphylococcus cohnii clinical isolate.
Methods: The species identification for methicillin-resistant S. cohnii clinical isolate WC28 was performed by sequencing the 16s rDNA gene. The detection of mecA gene and typing for SCCmec were carried out using multiplex PCR (mPCR) as described previously (J Clin Microbiol 2005; 43: 502633.). Universal primers for amplifying ccrA and ccrB genes were designed on the basis of the sequence alignment of all known variants, which were retrieved from GenBank. A universal primer for left side inverted repeat (IR-L) of SCCmec was deigned according to known variants of SCCmec. The whole SCCmec was obtained by three long-range PCR (Fermentas, Burlington, ON, Canada) amplifying regions from mecA to orfX, from ccrA/B to mecA and from IR-L to ccrA/B and sequencing. The sequence close to IR-L was identified using inverse PCR and HindIII-restricted WC28 genomic DNA was self-ligated and used as template.
Results: WC28 can grow on agar plates containing 4 mg/L cefoxitin and has a class A mecA complex (mecI-mecR1-mecA). However, SCCmec of WC28 can not be typed by the mPCR method used, suggesting that WC28 might harbor a new SCCmec element. The ccrA and ccrB genes of WC28 were obtained using the newly-designed universal primers and displayed the highest similarity (89%) with ccrASHP (GenBank accession no. EU934095) of Staphylococcus haemolyticus and ccrB5 (AM904731) of Staphylococcus pseudintermedius, respectively. The SCCmec of WC28 was fully characterized, ca. 35-kb in length, flanked by 8-bp perfect IR and generating 12-bp direct target repeat. Several new ORFs including a putative AAA-ATPase-encoding gene were identified in the J1 region (from IR-L to ccr). The J2 region (from ccr to mec) is almost identical to the corresponding part of SCCmec III (AB037671) and has a PsiTn554 transposon, while the J3 region (from mecA to orfX) is the same as that in SCCmec type IV (AB063172) containing a single copy of IS431.
Conclusions: WC28 has a new SCCmec element sharing similar features with several known SCCmec including Type III and IV. As the structure downstream of mecA in WC28 is also seen in a few different types of SCCmec and type III SCCmec appears to be a hybrid of two different SCC elements, the SCCmec of WC28 might be an ancestral structure of the widespread type III SCCmec in the methicillin-resistant Staphylococcus aureus.
|Session name:||Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases|
|Location:||Vienna, Austria, 10 - 13 April 2010|
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