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Livestock-associated MRSA lack accessory virulence determinants of human-associated MRSA

ABSTRACT: Previous studies have documented the diversity of genetic background of methicillin-resistant S. aureus (MRSA) strains associated with healthcare (HA-MRSA), community (CA-MRSA) and livestock (LA-MRSA). The accessory and core-variable genome content of those strains remain largely unknown. To compare the composition of accessory and core-variable genome of Belgian MRSA strains according to host, population setting and genetic background, representative strains of HA- (n=21), CA- (n = 13) and ST398 LA-MRSA (n = 18) were characterized by a DNA-microarray (StaphVar Array) composed of oligonucleotide probes targeting ~400 resistance, adhesion and virulence associated genes.ST398 strains displayed very homogenous hybridization profiles (>94% gene content homology) irrespective of their host origin. This “ST398-specific” genomic profile was not distantly demarked from those of certain human-associated lineages but lacked several virulence- and colonization-associated genes harbored by strains of human origin, such as genes encoding proteases, haemolysins or adhesins. No enterotoxin gene was found among ST398 strains. In conclusion, our findings are consistent with a non-human origin of this ST398 lineage but suggest that it might have the potential to adapt further to the human host.

ORGANISM(S): Staphylococcus aureus

PROVIDER: GSE20541 | GEO | 2010/11/15

SECONDARY ACCESSION(S): PRJNA125295

REPOSITORIES: GEO

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Project description:Approximatively 75% of the genome of S. aureus (“core” genome) are highly conserved between strains, whereas the remaining 25% (“accessory” genome) are composed of variable regions that are mostly composed of mobile genetic elements (MGE), containing virulence and resistance genes. We have developed a composite DNA-microarray (StaphVar Array) which selectively targets 403 genes located on the accessory or core variable genome. Target genes encode antimicrobial resistance factors (35 %), virulence factors (28 %) and adhesins (31%). This microarray was validated with reference strains and used to characterize the genomic DNA of 13 community-acquired methicillin resistant S. aureus (CA-MRSA) strains representative of all the Multilocus Sequence Types (STs) described to date in Belgium. Analysis of gene content of 8 reference strains by the StaphVar Array matched 96 to 99% of the theoretical results. Analysis of CA-MRSA strains showed that 54.4 % of the genes tested were strain-dependent. Strains presented specific exotoxin, enterotoxin, cytolysin and adhesin gene profile by multi-locus sequence typing (MLST) lineage. One exception to these “lineage-specific” gene profile was the variable presence of the Arginin Catabolic Mobile Element (ACME, characteristic of the USA300 clone) within ST8 strains. In conclusion, this novel StaphVar array enables characterization of more than 400 variable resistance and virulence determinants in S. aureus strains. CA-MRSA strains from Belgium displayed extensive diversity in virulence and resistance profile. The presence of the USA 300 clone in our country was confirmed. Although mainly located on MGE, association of virulence genes were highly conserved within strains of the same MLST lineage. CGH microarray was performed on 13 epidemiologically distinct clinical isolates of methicillin resistant S. aureus. S. aureus labeled genomic DNA were hybridized to StaphVar arrays containing 1326 60mer oligonucleotide probes (Eurogentec, Belgium).

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Livestock-associated MRSA lack accessory virulence determinants of human-associated MRSA

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