Department of Clinical Sciences, St George's, University of London, Cranmer Terrace, London SW17 0RE, UK.
J Antimicrob Chemother. 2012 Oct;67(10):2514-22. doi: 10.1093/jac/dks245. Epub 2012 Jul 3.
The majority of HA-MRSA infections are caused by endogenous infection and by only a small number of clones. The reasons for the success of some clones over others are unknown.
We investigated the evolution of an MRSA population from a large, acute-care teaching hospital in London, UK over a 10 year period. MRSA incidence and antibiotic prescribing were correlated with changes in resistance genes and prevalence of clonal groups.
Three clones caused the majority of infections, CC30 SCCmecII (EMRSA-16), CC22 SCCmecIV (EMRSA-15) and ST239 SCCmecIII. Clones that were multidrug resistant were selected for, and CC22 became dominant once it acquired a wide range of extra resistance genes. CC22 MRSA was also the fittest clone in an independent growth assay and a competition assay, and had a greater ability to survive desiccation. No individual isolate was fully drug resistant, and there was evidence of substantial horizontal gene transfer (HGT) as well as resistance gene loss within the clonal groups. The exception was fluoroquinolone resistance, which was rarely lost by any of the dominant hospital clones, suggesting that this resistance contributes to selection and survival of HA-MRSA. In support of this, a decrease in hospital-wide ciprofloxacin (a fluoroquinolone) prescribing was strongly associated with an overall decrease in MRSA infection.
Our data suggest successful HA-MRSA clones such as CC22 SCCmecIV are resistant to fluoroquinolones as well as fitter and able to acquire, but not necessarily accumulate, resistance to a wide range of additional antibiotics.
大多数 HA-MRSA 感染是由内源性感染和少数几个克隆引起的。一些克隆成功的原因尚不清楚。
我们调查了来自英国伦敦一家大型急性护理教学医院的 MRSA 人群在 10 年期间的演变。MRSA 发病率和抗生素处方与耐药基因的变化和克隆群的流行相关。
三个克隆引起了大多数感染，CC30 SCCmecII（EMRSA-16），CC22 SCCmecIV（EMRSA-15）和 ST239 SCCmecIII。对多药耐药的克隆进行了选择，一旦 CC22 获得了广泛的额外耐药基因，它就成为了优势克隆。CC22 耐甲氧西林金黄色葡萄球菌在独立生长试验和竞争试验中也是最适应的克隆，并且具有更强的干燥生存能力。没有单个分离株是完全耐药的，并且在克隆群内有大量的水平基因转移（HGT）和耐药基因丢失的证据。例外是氟喹诺酮类耐药性，任何主要的医院克隆都很少丢失，这表明这种耐药性有助于选择和生存 HA-MRSA。支持这一点的是，医院范围内环丙沙星（氟喹诺酮类）处方的减少与 MRSA 感染的总体减少密切相关。
我们的数据表明，成功的 HA-MRSA 克隆，如 CC22 SCCmecIV，对氟喹诺酮类药物具有耐药性，并且更适应，能够获得，但不一定积累，对广泛的其他抗生素的耐药性。
