Department of Zoology, University of Oxford, Oxford, UK.
ISME J. 2010 Apr;4(4):577-84. doi: 10.1038/ismej.2009.151. Epub 2010 Jan 14.
The prevalence of diverse MRSA (methicillin-resistant Staphylococcus aureus) types in both hospital and community settings is a major health problem worldwide. Here we compare hospital-acquired MRSAs with large type II SCCmec elements with those prevalent in both hospital and community settings with smaller type IV SCCmec elements. We find that the type II but not the type IV SCCmec element causes the bacteria to reduce their levels of costly toxin expression. We compare the relative growth rates of these MRSA types and show that the type II SCCmec carrying MRSAs are more affected than those carrying type IV elements and from this we hypothesize that offsetting the costs associated with antibiotic resistance and toxin expression is why the type II are confined to hospital environments where antibiotic use, the prevalence of immunocompromised individuals and vector-mediated transmission is high. In contrast, those MRSAs that are also successful in the community can maintain their high levels of toxin expression due to a lower fitness burden associated with the smaller SCCmec element.
不同类型耐甲氧西林金黄色葡萄球菌（MRSA）在医院和社区环境中的流行是一个全球性的主要健康问题。在这里，我们将医院获得性携带大型 II 型 SCCmec 元件的 MRSAs 与在医院和社区环境中流行的携带较小的 IV 型 SCCmec 元件的 MRSAs 进行了比较。我们发现，只有 II 型 SCCmec 元件而不是 IV 型 SCCmec 元件会导致细菌降低其昂贵毒素表达的水平。我们比较了这些 MRSA 类型的相对增长率，并表明携带 II 型 SCCmec 的 MRSAs 比携带 IV 型元素的 MRSAs 受到更大的影响，因此我们假设，与抗生素耐药性和毒素表达相关的成本是 II 型仅局限于医院环境的原因，在医院环境中，抗生素的使用、免疫功能低下个体的流行和媒介传播的情况很高。相比之下，那些在社区中也能成功生存的 MRSAs 由于与较小的 SCCmec 元件相关的较低适应性负担，可以维持其高水平的毒素表达。
