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Characterization of the factors asso...

Noto, Michael James.

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Characterization of the factors associated with SCCmec mobility in Staphylococcus aureus.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Characterization of the factors associated with SCCmec mobility in Staphylococcus aureus./
作者:	Noto, Michael James.
面頁冊數:	164 p.
附註:	Adviser: Gordon L. Archer.
Contained By:	Dissertation Abstracts International68-07B.
標題:	Biology, Microbiology. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3270228
ISBN:	9780549088790

Characterization of the factors associated with SCCmec mobility in Staphylococcus aureus.
Noto, Michael James.

Characterization of the factors associated with SCCmec mobility in Staphylococcus aureus. - 164 p.

Adviser: Gordon L. Archer.

Thesis (Ph.D.)--Virginia Commonwealth University, 2007.

The gene encoding resistance to beta-lactam antibiotics in the staphylococci is found on the chromosome in a genomic island designated Staphylococcal Chromosome Cassette mec, or SCCmec. In addition to the resistance gene, mecA, SCCmec also contains site specific recombinase genes, ccrAB, that are capable of catalyzing the chromosomal excision and integration of SCCmec. The increasing prevalence of methicillin-resistant Staphylococcus aureus infections may be due, in part, to the transfer of SCC mec into successful methicillin-sensitive S. aureus lineages. In this work we attempt to better characterize the factors associated with SCCmec transfer, beginning with CcrAB-mediated SCC mec excision in a collection of MRSA containing type IV SCC mec. CcrAB-mediated excision of type IV SCCmec was not demonstrated for all strains tested, as a subset of S. aureus strains with type IV SCCmec did not excise their element. These strains are all highly related and represent a lineage of successful community associated pathogens. In addition, the inability to excise SCC mec in these strains is associated with the presence of a presumptive mobile element containing the gene for staphylococcal enterotoxin H ( seh) immediately outside of SCCmec on the chromosome. Staphylococcus aureus strain USA300 contains SCCmec type IV and a genomic island containing an arginine deiminase pathway, known as ACME, inserted adjacent to one another in the SCCmec chromosomal attachment site. Each element was site-specifically excised from the chromosome by CcrAB, resulting in two independent, extra-chromosomal, circularized elements. Therefore the presence of ACME did not disrupt SCCmec excision.

ISBN: 9780549088790Subjects--Topical Terms:

1017734
Biology, Microbiology.

Characterization of the factors associated with SCCmec mobility in Staphylococcus aureus.
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245 1 0 $a Characterization of the factors associated with SCCmec mobility in Staphylococcus aureus.
300 $a 164 p.
500 $a Adviser: Gordon L. Archer.
500 $a Source: Dissertation Abstracts International, Volume: 68-07, Section: B, page: .
502 $a Thesis (Ph.D.)--Virginia Commonwealth University, 2007.
520 $a The gene encoding resistance to beta-lactam antibiotics in the staphylococci is found on the chromosome in a genomic island designated Staphylococcal Chromosome Cassette mec, or SCCmec. In addition to the resistance gene, mecA, SCCmec also contains site specific recombinase genes, ccrAB, that are capable of catalyzing the chromosomal excision and integration of SCCmec. The increasing prevalence of methicillin-resistant Staphylococcus aureus infections may be due, in part, to the transfer of SCC mec into successful methicillin-sensitive S. aureus lineages. In this work we attempt to better characterize the factors associated with SCCmec transfer, beginning with CcrAB-mediated SCC mec excision in a collection of MRSA containing type IV SCC mec. CcrAB-mediated excision of type IV SCCmec was not demonstrated for all strains tested, as a subset of S. aureus strains with type IV SCCmec did not excise their element. These strains are all highly related and represent a lineage of successful community associated pathogens. In addition, the inability to excise SCC mec in these strains is associated with the presence of a presumptive mobile element containing the gene for staphylococcal enterotoxin H ( seh) immediately outside of SCCmec on the chromosome. Staphylococcus aureus strain USA300 contains SCCmec type IV and a genomic island containing an arginine deiminase pathway, known as ACME, inserted adjacent to one another in the SCCmec chromosomal attachment site. Each element was site-specifically excised from the chromosome by CcrAB, resulting in two independent, extra-chromosomal, circularized elements. Therefore the presence of ACME did not disrupt SCCmec excision.
520 $a Next, we describe three MRSA strains that became resistant to vancomycin during passage on increasing concentrations of the drug. In each case, mecA was lost during passage. Strain 5836VR lost mecA by the site-specific chromosomal excision of SCCmec while the other two strains (3130VR and VP32) deleted portions of their SCC mec elements in a manner that appears to involve IS431. Conversion to vancomycin resistance caused a decrease in growth rate that was partially compensated for by deletion of mecA. In mixed culture competition experiments, vancomycin resistant strains that lacked mecA readily out-competed their mecA-containing counterparts, suggesting that the loss of mecA during conversion to vancomycin resistance was advantageous to the organism.
520 $a Finally, we examined the genetic structure surrounding the SCC mec attachment site in a diverse collection of methicillin-sensitive S. aureus isolates. This region of the chromosome varies greatly from strain to strain and appears to be prone to recombination. Open reading frames found in this region were homologous to enterotoxins, restriction-modification enzymes, and transposases. Several open reading frames that have not been previously reported in staphylococci were also present in this region. 28 out of the 42 isolates examined did not contain the attachment site sequence found in S. aureus isolates known to be capable of CcrAB-mediated SCCmec integration or excision. This may indicate that these strains do not contain a functional attachment site and therefore may not have the potential to acquire SCCmec by CcrAB-mediated recombination.
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