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dc.contributor.authorGallagher, Laura A.
dc.contributor.authorCoughlan, Simone
dc.contributor.authorBlack, Nikki S.
dc.contributor.authorLalor, Pierce
dc.contributor.authorWaters, Elaine M.
dc.contributor.authorWee, Bryan
dc.contributor.authorWatson, Mick
dc.contributor.authorDowning, Tim
dc.contributor.authorFitzgerald, J. Ross
dc.contributor.authorFleming, Gerard T. A.
dc.contributor.authorO'Gara, James P.
dc.date.accessioned2018-09-20T16:08:47Z
dc.date.available2018-09-20T16:08:47Z
dc.date.issued2017-07-17
dc.identifier.citationGallagher, Laura A. Coughlan, Simone; Black, Nikki S.; Lalor, Pierce; Waters, Elaine M.; Wee, Bryan; Watson, Mick; Downing, Tim; Fitzgerald, J. Ross; Fleming, Gerard T. A.; O'Gara, James P. (2017). tandem amplification of the staphylococcal cassette chromosome mec element can drive high-level methicillin resistance in methicillin-resistant staphylococcus aureus . Antimicrobial Agents and Chemotherapy 61 (9),
dc.identifier.issn0066-4804,1098-6596
dc.identifier.urihttp://hdl.handle.net/10379/11576
dc.description.abstractHospital-associated methicillin-resistant Staphylococcus aureus (MRSA) strains typically express high-level, homogeneous (HoR) beta-lactam resistance, whereas community-associated MRSA (CA-MRSA) more commonly express low-level heterogeneous (HeR) resistance. Expression of the HoR phenotype typically requires both increased expression of the mecA gene, carried on the staphylococcal cassette chromosome mec element (SCCmec), and additional mutational event(s) elsewhere on the chromosome. Here the oxacillin concentration in a chemostat culture of the CA-MRSA strain USA300 was increased from 8 mu g/ml to 130 mu g/ml over 13 days to isolate highly oxacillin-resistant derivatives. A stable, small-colony variant, designated HoR34, which had become established in the chemostat culture was found to have acquired mutations in gdpP, clpX, guaA, and camS. Closer inspection of the genome sequence data further revealed that reads covering SCCmec were similar to 10 times overrepresented compared to other parts of the chromosome. Quantitative PCR (qPCR) confirmed >10-fold-higher levels of mecA DNA on the HoR34 chromosome, and MinION genome sequencing verified the presence of 10 tandem repeats of the SCCmec element. qPCR further demonstrated that subculture of HoR34 in various concentrations of oxacillin (0 to 100 mu g/ml) was accompanied by accordion-like contraction and amplification of the SCCmec element. Although slower growing than strain USA300, HoR34 outcompeted the parent strain in the presence of subinhibitory oxacillin. These data identify tandem amplification of the SCCmec element as a new mechanism of high-level methicillin resistance in MRSA, which may provide a competitive advantage for MRSA under antibiotic selection.
dc.publisherAmerican Society for Microbiology
dc.relation.ispartofAntimicrobial Agents and Chemotherapy
dc.subjectcontinuous culture
dc.subjectsccmec
dc.subjectstaphylococcus
dc.subjectantibiotic resistance
dc.subjectbeta-lactams
dc.subjectmeca beta-lactam
dc.subjectantibiotic
dc.subjectresistance
dc.subjectmechanism
dc.subjectnanopore sequencing data
dc.subjectantibiotic-resistance
dc.subjectgenome
dc.subjectusa300
dc.subjectcost
dc.subjectvancomycin
dc.subjectillumina
dc.subjectdeletion
dc.subjectclone
dc.titletandem amplification of the staphylococcal cassette chromosome mec element can drive high-level methicillin resistance in methicillin-resistant staphylococcus aureus
dc.typeArticle
dc.identifier.doi10.1128/aac.00869-17
dc.local.publishedsourcehttp://europepmc.org/articles/pmc5571284?pdf=render
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