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Comparative virulence studies and transcriptome analysis of Staphylococcus aureus strains isolated from animals

ABSTRACT: Staphylococcus aureus can infect a wide range of animals and pose as a serious threat to public health by transferring via animals or animal-derived food stuff. Even more importantly, multiple drug resistance development in the bacteria has resulted in therapeutic failure of a number of antibiotics. Therefore by realizing the need of time, this study was designed to investigate the underlying mechanisms of virulence and resistance in S. aureus. After screening through in vivo and in vitro virulence assays and susceptibility test, a highly virulent and multidrug resistant MRSA strain was selected for differential analysis by RNA-seq technology and gene expression results were verified by RT-qPCR. Up-regulation of crucial regulators like sarA and KdpDE seemed to play role in decreased expression of many exotoxin genes while enhanced the adhesion and cell wall protein expression, leading to strong biofilm production in the presence of inactivated agr system. In addition to resistance genes like blaZ, ermC and femA, up-regulation of vraS and multidrug ABC transporter genes contributed to the multidrug resistance in MRSA. Fluoroquinolone resistance was attributed to mutational changes in gyrA and parC genes. Our findings suggested that many virulence and resistance determinants in S. aureus are controlled by complex network of various regulators, and sarA is the most important of those as it adds to pathogenicity of the bacteria and ensures its survival in diverse environment. Further investigations are required to unveil these mechanisms in S. aureus.

ORGANISM(S): Staphylococcus aureus

PROVIDER: GSE78764 | GEO | 2016/03/02

SECONDARY ACCESSION(S): PRJNA313454

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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Comparative virulence studies and transcriptome analysis of Staphylococcus aureus strains isolated from animals

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