活跃的MRSA传播

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检索丨陈志锦

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最新数据表明，耐甲氧西林金黄色葡萄球菌（MRSA）病房感控措施在解决医院和社区中以病人为中心的传播途径问题上存在不足。

英国伦敦卫生和热带医学学院的研究员Francesc Coll博士及其同事分析了MRSA的基因组，发现三个具有说服力的流行病学环节：共同的邮政编码、共同的全科医生和共同的病房接触，除了事故和急救部门外。


科尔博士和同事写道：“我们的研究结果对感染控制政策和实践有着重要的影响，我们研究人群中的MRSA传播不是归因于大型医院爆发，而是由于许多临床无法识别的“插曲”的累积影响，我们检测到173个单独的遗传簇，在12个月的时间里映射到许多不同的地点，这表明感染控制的反复失效。” 他们在10月25日的《科学转化医学》杂志上发表了他们的研究成果。


调查人员在英格兰东部进行了一年的流行病学调查，分析了三家医院的样本和75名全科医生的执业范围， 患者平均年龄68岁。


研究人员对MRSA分离物进行了测序，并从1465名患者中识别出至少一个MRSA分离株，共有2282个MRSA分离株。 然后使用基因组比较将分离株分配到个传播簇，他们能将40.8％的患者分配到包含2到44例的173个传播簇。

当他们将每种病例与MRSA分离株最接近遗传匹配的个体配对时，发现细菌相关性与流行病学接触强度之间存在直接联系。


他们写道：“通过包括病人的流行病学资料，我们发现住宅邮政编码和全科医师注册信息是MRSA传播中具有说服力流行病学标志。 由两名或多名MRSA阳性患者共享相同的邮政编码或全科医生经常预示着暴发，其中一些跨越了几个月。”但研究人员没有进行纵向追踪或出院MRSA筛查，也没有对环境蓄水池和医护人员进行检测。


大多数感染控制专家认为，有两种类型的MRSA谱系：一种适应于医院的持续传播，另一种则与其他金黄色葡萄球菌竞相传播至整个社区。 来自Dr. Coll及其同事的新资料则显示，社区相关和医院相关的MRSA谱系都能够在整个社区传播。


他们写道：“为在英格兰东部进入同一个医疗转诊网络的人口进行综合流行病学和基因组监测的价值提供证据。 这样的研究可能揭示着，目前的感染控制政策和做法可能并不是最合适的。
 原文：MRSA: Community and Hospital Transmission Common, Study ShowsNew data suggest that a ward-based approach to methicillin-resistant Staphylococcus aureus (MRSA) infection control is inadequate to address patient-centric transmission in hospitals and communities.


When Francesc Coll, PhD, research fellow at the London School of Hygiene and Tropical Medicine in the United Kingdom, and colleagues analyzed genomic clusters of MRSA, they found three strong epidemiological links: shared post codes, shared general practitioner practice, and shared ward contacts other than the accident and emergency department.


"Our findings have important implications for infection control policy and practice," Dr Coll and colleagues write. "MRSA transmission in our study population was not attributable to large nosocomial outbreaks but resulted from the cumulative effect of numerous clinically unrecognized episodes. We detected 173 separate genetic clusters that mapped to numerous different locations over the course of 12 months, which is indicative of repeated lapses in infection control." They published their results in the October 25 issue of Science Translational Medicine.


The investigators performed their epidemiological study during a 1-year period in the east of England, analyzing samples from three hospitals and 75 general practitioner practices. Patients had a mean age of 68 years.


The researchers sequenced the MRSA isolates and identified at least one MRSA isolate from 1465 individuals for a total of 2282 MRSA isolates. Using genome comparisons to assign the isolates to clusters, they were able to assign 40.8% of the patients to 173 transmission clusters containing between 2 and 44 cases.


When they paired each case with the individual whose MRSA isolate was the closest genetic match, they found a direct relationship between bacterial relatedness and strength of epidemiological contact.


"By including patient epidemiological information, we found that residential postcodes and [general pratitioner] registration information were strong epidemiological markers of MRSA transmission," they write. "Sharing the same postcode or [general practitioner] practice by two or more MRSA-positive patients often indicated an outbreak, some of which spanned several months."


The researchers did not track longitudinal or discharge MRSA screening in hospitals, nor did they screen environmental reservoirs and healthcare workers.


Most infectious control experts believe there are two types of MRSA lineages: one that adapts to persist and spread in hospitals and another that successfully competes with other S aureus lineages to spread throughout the community. The new data from Dr Coll and colleagues indicate that both community-associated and hospital-associated MRSA lineages are capable of transmission throughout the community.


"[W]e provide evidence for the value of integrated epidemiological and genomic surveillance of a population that accesses the same health care referral network in the East of England," they write. Such research may reveal, as theirs has, that current infection control policy and practice may be inappropriate.


One author is on the advisory board for Discuva Ltd. Two others are paid consultants for Specific Technologies.
Sci Transl Med. 2017:9:eaak9745. Abstract 
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