Livestock-associated MRSA lack accessory virulence determinants of human-associated MRSA. Staphylococcus aureus

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. Overall design: CGH microarray was performed on epidemiologically distinct human and animal isolates of methicillin resistant S.aureus. S. aureus labeled genomic DNA were hybridized to StaphVar arrays containing 1326 60mer oligonucleotide probes (Eurogentec, Belgium).

已有研究表明，与医疗保健相关的耐甲氧西林金黄色葡萄球菌（methicillin-resistant S. aureus, MRSA）菌株、社区相关性MRSA（community-associated MRSA, CA-MRSA）及畜禽相关性MRSA（livestock-associated MRSA, LA-MRSA）均存在多样化的遗传背景。目前，此类菌株的附属基因组与核心可变基因组组成仍未得到充分解析。为对比不同宿主、人群环境及遗传背景下比利时MRSA菌株的附属基因组与核心可变基因组组成，研究人员选取医疗相关性MRSA（n=21）、社区相关性MRSA（n=13）及ST398型畜禽相关性MRSA（n=18）的代表性菌株，采用由靶向约400个耐药、黏附及毒力相关基因的寡核苷酸探针构建的DNA微阵列（StaphVar Array）进行表征分析。ST398型菌株无论宿主来源如何，均呈现高度一致的杂交图谱（基因内容同源性＞94%）。该“ST398特异性”基因组特征与部分人类相关性谱系的基因组特征并无显著差异，但缺失人类来源菌株所携带的若干毒力及定植相关基因，例如编码蛋白酶、溶血素或黏附素的基因。ST398型菌株中未检出任何肠毒素基因。综上，本研究结果支持ST398谱系起源于非人类宿主，但提示该谱系具备进一步适应人类宿主的潜力。整体实验设计：本研究针对流行病学特征各异的人类及动物来源耐甲氧西林金黄色葡萄球菌分离株，开展比较基因组杂交（comparative genomic hybridization, CGH）微阵列实验。将经荧光标记的金黄色葡萄球菌基因组DNA，与包含1326条60聚体寡核苷酸探针的StaphVar微阵列进行杂交（探针由比利时欧根泰克（Eurogentec）公司合成）。