Characterization of the staphylococcal cassette chromosome composite island of Staphylococcus haemolyticus SH32, a methicillin-resistant clinical isolate from China.
Staphylococcal cassette chromosome (SCC) elements contribute considerably to virulence and resistance to antibiotic agents in staphylococci. SCC elements in coagulase-negative staphylococci (CoNS) are highly diverse and there is evidence suggesting that they serve as a reservoir for antibiotic resistance genes in methicillin-resistant Staphylococcus aureus (MRSA). However, only a small number of SCC elements have been characterized in CoNS and their exact roles in the emergence and evolution of MRSA remain to be demonstrated. Here, we determined the structure of an SCC composite island (CISH32) found in the clinical Staphylococcus haemolyticus isolate SH32 by whole-genome DNA sequencing. CISH32 was 48 kb in length and mainly composed of two imperfect SCC elements, namely (i) a ΨSCCmec(SH32) part containing a class C1 mec gene complex but lacking ccr genes and (ii) a SCCSH32 part with a ccrA5B3 gene complex but lacking mec genes. In addition, CISH32 contained a type III restriction-modification system and several resistance loci, for example genes conferring resistance to cadmium and arsenic. ΨSCCmec(SH32) is almost entirely identical to a pseudo SCCmec element found in S. haemolyticus WCH1 and shares pronounced sequence similarity to a ΨSCCmec element of S. haemolyticus JCSC1435. However, staphylococci other than S. haemolyticus, including S. aureus and S. epidermidis, contain homologs of SCCSH32 that are more similar to SCCSH32 than those elements found in S. haemolyticus, suggesting that CISH32 of S. haemolyticus SH32 was assembled in recent evolutionary events. Moreover, the composite structure of CISH32 indicates that the detection of class C1 mec and ccrA5B3 gene complexes in S. haemolyticus does not always indicate the existence of a UT9-type SCCmec element, which has remained questionable.
Institute of Developmental and Regenerative Biology, Hangzhou Normal University, Hangzhou, China ; Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China.
Dongliang
D
Yu
Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China.
Borui
B
Pi
Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China ; National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland, United States of America.
Yan
Y
Chen
Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China.
Yanfei
Y
Wang
Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China.
Zhi
Z
Ruan
National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland, United States of America.
Michael
M
Otto
Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China.
Yunsong
Y
Yu
D001483:Base Sequence; D002681:China; D019295:Computational Biology; D017931:DNA Primers / Q000235:genetics; D019143:Evolution, Molecular; D016680:Genome, Bacterial / Q000235:genetics*; D044404:Genomic Islands / Q000235:genetics*; D016106:Methicillin Resistance / Q000235:genetics*; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D013045:Species Specificity; D041162:Staphylococcus haemolyticus / Q000235:genetics*
D017931:DNA Primers