Aires de Sousa Marta, de Lencastre Hermínia
Laboratório de Genética Molecular, Instituto de Tecnologia Química e Biológica da Universidade Nova de Lisboa, Oeiras, Portugal.
FEMS Immunol Med Microbiol. 2004 Mar 8;40(2):101-11. doi: 10.1016/S0928-8244(03)00370-5.
Methicillin-resistant Staphylococcus aureus (MRSA) emerged in the early 1960's after the acquisition of the methicillin resistance gene mecA, which is carried by the staphylococcal cassette chromosome mec (SCCmec). MRSA seemed to have arisen by multiple introductions of SCCmec into successful methicillin-susceptible S. aureus (MSSA) lineages. MRSA is one of the most common agents of nosocomial infections worldwide increasing the cost and mortality compared to MSSA infections. Little by little, MRSA has acquired resistance to all antibiotics available in clinical practice, which complicates treatment. This situation was further aggravated by the recent reports of vanA-mediated vancomycin-resistant S. aureus. As a reaction to the emergence and spread of multidrug-resistant MRSA worldwide, international surveillance systems such as the CEM/NET initiative have been created. The characterization of over 3000 MRSA isolates from different regions of the world evidenced the existence of only a few epidemic clones spread worldwide, namely the Iberian, Brazilian, Hungarian, New York/Japan, Pediatric and EMRSA-16 clones. It was found that in surveillance or evolutionary studies strains should be characterized by a combination of different typing methods, namely pulsed-field gel electrophoresis, multi-locus sequence typing and SCCmec typing. In recent years, community-acquired MRSA (CA-MRSA) has become a growing public health concern. However, although many authors reported the emergence of CA-MRSA isolates, a standard definition has not been created and the prevalence of MRSA among persons without risk factors seems to remain very low. CA-MRSA has distinct properties compared to epidemic nosocomial clones and its origin is still unclear. Certain authors suggest there is MRSA transmission from the hospital setting to the community, namely transfer of nosocomial MRSA minor clones or sporadic isolates showing a high degree of similarity with CA-MRSA; others believe CA-MRSA strains represent new acquisitions of SCCmec DNA in susceptible backgrounds. Many questions concerning this extraordinarily versatile and threatening pathogen remain unanswered, needing future investigation
耐甲氧西林金黄色葡萄球菌（MRSA）于20世纪60年代初出现，是在获得甲氧西林抗性基因mecA之后出现的，该基因由葡萄球菌盒式染色体mec（SCCmec）携带。MRSA似乎是通过将SCCmec多次引入成功的甲氧西林敏感金黄色葡萄球菌（MSSA）谱系中产生的。MRSA是全球医院感染最常见的病原体之一，与MSSA感染相比，增加了成本和死亡率。渐渐地，MRSA对临床实践中可用的所有抗生素都产生了抗性，这使得治疗变得复杂。最近关于vanA介导的万古霉素抗性金黄色葡萄球菌的报道进一步加剧了这种情况。作为对全球多药耐药MRSA出现和传播的反应，已经建立了诸如CEM/NET倡议等国际监测系统。对来自世界不同地区的3000多株MRSA分离株的特征分析表明，全球仅存在少数流行克隆，即伊比利亚、巴西、匈牙利、纽约/日本、儿科和EMRSA-16克隆。研究发现，在监测或进化研究中，菌株应以不同分型方法的组合进行特征分析，即脉冲场凝胶电泳、多位点序列分型和SCCmec分型。近年来，社区获得性MRSA（CA-MRSA）已成为一个日益严重的公共卫生问题。然而，尽管许多作者报道了CA-MRSA分离株的出现，但尚未形成标准定义，而且在没有危险因素的人群中MRSA的流行率似乎仍然很低。与医院流行克隆相比，CA-MRSA具有不同的特性，其起源仍不清楚。某些作者认为存在从医院环境到社区的MRSA传播，即医院MRSA小克隆或散发病例分离株的转移，这些分离株与CA-MRSA表现出高度相似性；另一些人则认为CA-MRSA菌株代表了在敏感背景下新获得的SCCmec DNA。关于这种极其通用且具有威胁性的病原体的许多问题仍然没有答案，需要未来进行研究。
