SCCmec explained

SCCmec, or staphylococcal cassette chromosome mec, is a mobile genetic element of Staphylococcus bacterial species. This genetic sequence includes the mecA gene coding for resistance to the antibiotic methicillin and is the only known way for Staphylococcus strains to spread the gene in the wild by horizontal gene transfer.[1] SCCmec is a 21 to 60 kb long genetic element that confers broad-spectrum β-lactam resistance to MRSA.[2] Moreover, additional genetic elements like Tn554, pT181, and pUB110 can be found in SCCmec, which have the capability to render resistance to various non-β-lactam drugs.[3]

Classification

Not all SCCmec elements are identical (in fact, SCC elements without the mecA gene do exist.[4]) As of December 2021, SCCmec elements have been classified into fourteen types (I through XIV).[5] One region is the mec complex including the mecA gene. The other is the ccr gene complex including genes coding for recombinases.[6]

The mec complex is divided further into five types (I through V) based on the arrangement of regulatory genetic features such as mecR1, an inducer.[7] The mec gene complex in SCCmec, comprising mec gene, its regulators (mecR1, mecI), and insertion sequences (IS), is categorized into five classes (A to E). Class A includes mecA, full mecR1, mecI, and IS431. Class B has IS1272, mecA, partial mecR1, and IS431. Class C, with two versions (C1, C2), contains mecA, partial mecR1, IS431, differing in IS431 orientation. Class D includes IS431, mecA, partial mecR1; Class E consists of blaZ, mecC, mecR1, mecI.[8] [9]

The ccr and mec gene complexes in SCCmec are connected by joining (J) regions, considered non-essential but capable of carrying extra antimicrobial resistance determinants.[10] [11] These are categorized as J1, J2, and J3, based on their SCCmec positions. J1, also known as the L-C region, lies between the right chromosomal junction and upstream of the ccr gene. J2, previously the C-M region, is situated between the ccr and mec gene complexes. J3 (formerly the I-R region) is found downstream of the mec gene complex, extending to the left chromosomal junction.[12]

Distribution

The SCCmec found in methicillin-resistant Staphylococcus aureus likely originated in coagulase-negative staphylococcal species and was acquired by S. aureus.[13]

Staphylococcal strains isolated from pig farms were found to carry several different types of SCCmec, suggesting that they may serve as a reservoir of these elements.[14]

See also

Notes and References

  1. Hanssen AM, Ericson Sollid JU . SCCmec in staphylococci: genes on the move . FEMS Immunology and Medical Microbiology . 46 . 1 . 8–20 . February 2006 . 16420592 . 10.1111/j.1574-695X.2005.00009.x . 37999833 . free .
  2. Katayama Y, Ito T, Hiramatsu K . A new class of genetic element, staphylococcus cassette chromosome mec, encodes methicillin resistance in Staphylococcus aureus . Antimicrobial Agents and Chemotherapy . 44 . 6 . 1549–1555 . June 2000 . 10817707 . 89911 . 10.1128/AAC.44.6.1549-1555.2000 .
  3. Ito T, Hiramatsu K . Acquisition of methicillin resistance and progression of multiantibiotic resistance in methicillin-resistant Staphylococcus aureus . Yonsei Medical Journal . 39 . 6 . 526–533 . December 1998 . 10097679 . 10.3349/ymj.1998.39.6.526 . free .
  4. Hanssen AM, Ericson Sollid JU . SCCmec in staphylococci: genes on the move . FEMS Immunology and Medical Microbiology . 46 . 1 . 8–20 . February 2006 . 16420592 . 10.1111/j.1574-695X.2005.00009.x . free .
  5. Uehara Y . Current Status of Staphylococcal Cassette Chromosome mec (SCCmec) . Antibiotics . 11 . 1 . 86 . January 2022 . 35052963 . 8772726 . 10.3390/antibiotics11010086 . free .
  6. Hiramatsu K, Cui L, Kuroda M, Ito T . The emergence and evolution of methicillin-resistant Staphylococcus aureus . Trends in Microbiology . 9 . 10 . 486–493 . October 2001 . 11597450 . 10.1016/s0966-842x(01)02175-8 .
  7. Katayama Y, Ito T, Hiramatsu K . Genetic organization of the chromosome region surrounding mecA in clinical staphylococcal strains: role of IS431-mediated mecI deletion in expression of resistance in mecA-carrying, low-level methicillin-resistant Staphylococcus haemolyticus . Antimicrobial Agents and Chemotherapy . 45 . 7 . 1955–1963 . July 2001 . 11408208 . 90585 . 10.1128/AAC.45.7.1955-1963.2001 .
  8. Shore AC, Deasy EC, Slickers P, Brennan G, O'Connell B, Monecke S, Ehricht R, Coleman DC . 6 . Detection of staphylococcal cassette chromosome mec type XI carrying highly divergent mecA, mecI, mecR1, blaZ, and ccr genes in human clinical isolates of clonal complex 130 methicillin-resistant Staphylococcus aureus . Antimicrobial Agents and Chemotherapy . 55 . 8 . 3765–3773 . August 2011 . 21636525 . 3147645 . 10.1128/AAC.00187-11 .
  9. Classification of staphylococcal cassette chromosome mec (SCCmec): guidelines for reporting novel SCCmec elements . Antimicrobial Agents and Chemotherapy . 53 . 12 . 4961–4967 . December 2009 . 19721075 . 2786320 . 10.1128/aac.00579-09 .
  10. Classification of staphylococcal cassette chromosome mec (SCCmec): guidelines for reporting novel SCCmec elements . Antimicrobial Agents and Chemotherapy . 53 . 12 . 4961–4967 . December 2009 . 19721075 . 2786320 . 10.1128/AAC.00579-09 .
  11. Liu J, Chen D, Peters BM, Li L, Li B, Xu Z, Shirliff ME . Staphylococcal chromosomal cassettes mec (SCCmec): A mobile genetic element in methicillin-resistant Staphylococcus aureus . Microbial Pathogenesis . 101 . 56–67 . December 2016 . 27836760 . 10.1016/j.micpath.2016.10.028 .
  12. Lakhundi S, Zhang K . Methicillin-Resistant Staphylococcus aureus: Molecular Characterization, Evolution, and Epidemiology . Clinical Microbiology Reviews . 31 . 4 . October 2018 . 30209034 . 6148192 . 10.1128/CMR.00020-18 .
  13. Tsubakishita S, Kuwahara-Arai K, Sasaki T, Hiramatsu K . Origin and molecular evolution of the determinant of methicillin resistance in staphylococci . Antimicrobial Agents and Chemotherapy . 54 . 10 . 4352–4359 . October 2010 . 20679504 . 2944575 . 10.1128/AAC.00356-10 .
  14. Tulinski P, Fluit AC, Wagenaar JA, Mevius D, van de Vijver L, Duim B . Methicillin-resistant coagulase-negative staphylococci on pig farms as a reservoir of heterogeneous staphylococcal cassette chromosome mec elements . Applied and Environmental Microbiology . 78 . 2 . 299–304 . January 2012 . 22081567 . 3255757 . 10.1128/AEM.05594-11 . 2012ApEnM..78..299T .

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