Spread of Community-Acquired MRSA Among Household Contacts

描述(申请人提供)：流行社区获得的耐甲氧西林金黄色葡萄球菌(MRSA)是一种新出现的传染病，发生在以前健康的儿童和成人中，没有获得MRSA的危险因素。这些新的社区获得的MRSA(CA-MRSA)菌株与医院获得的MRSA(HA-MRSA)菌株的不同之处在于，它们通常对非B-内酰胺类抗生素敏感，引起的疾病类似于社区获得的甲氧西林敏感金黄色葡萄球菌(CA-MSSA)，并且含有编码细胞溶解毒素Panton-Valuine杀白素的基因。当对这些CA-MRSA菌株的抗生素敏感性模式的遗传因素进行表征时，人们意识到已经发生了一个独特的现象，不涉及HA-MRSA在社区中的传播。由CA-MRSA引起的皮肤和软组织感染、坏死性肺炎和败血症综合征的暴发已有越来越多的报道。我们正在寻求有关如何防止这些毒株传播以及如何治疗受感染和被殖民的个人的关键信息。CA-MRSA在家庭成员中定植的自然历史及其与感染的关系是必须确定的问题，以便制定有效的遏制、预防和治疗策略。为了确定CA-MRSA菌株的传播性，将对CA-MRSA病指示病例的家庭接触者进行CA-MRSA定植检测。家庭接触者的CA-MRSA携带率将与HA-MRSA指数患者的家庭接触者的HA-MRSA携带率进行比较。CA-MRSA菌株致病的频率将通过确定疾病的二次发作率进行前瞻性评估，并将与HA-MRSA进行比较。CA-MRSA的优势部位也将通过鼻子和手的培养来确定。所有菌株将通过脉冲场凝胶电泳、多位点序列分型、SCCmec分型和Luks-PV/lukF-PV聚合酶链式反应来确定CA-MRSA菌株的克隆谱系，并评估家庭接触者之间的相关性。从这项研究中获得的知识对于指导应对CA-MRSA疫情的进一步战略至关重要。确定指示病例的家庭接触者中的定植频率、CA-MRSA的二次发病率以及主要携带部位将有助于制定遏制、预防和治疗管理指南。

DESCRIPTION (provided by applicant): Epidemic Community-Acquired Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging infectious disease in previously healthy children and adults without risk factors for MRSA acquisition. These new community-acquired MRSA (CA-MRSA) strains differ from hospital-acquired MRSA (HA-MRSA) strains in that they are often susceptible to non-B-lactam antibiotics, cause disease similar to community-acquired methicillin-susceptible S. aureus (CA-MSSA), and contain the genes encoding the cytolytic toxin, Panton- Valentine leukocidin. When the genetic element responsible for the antibiotic susceptibility patterns in these CA-MRSA strains was characterized, now called "staphylococcal chromosomal cassette mec" type IV or SCCmec type IV, it was realized that a distinct phenomenon had occurred not involving spread of HA-MRSA into the community. Outbreaks of skin and soft tissue infections, necrotizing pneumonia, and sepsis syndromes due to CA-MRSA have been reported with increasing frequency. We are seeking crucial information on how to prevent spread of these strains and how to treat infected and colonized individuals. The natural history of CA-MRSA colonization among household members and its association with infection are issues that must be defined in order to develop effective containment, preventative, and therapeutic strategies. In order to define the transmissibility of CA-MRSA strains, household contacts of an index case with CA- MRSA disease will be tested for colonization by CA-MRSA. Rates of CA-MRSA carriage among household contacts will be compared with rates of HA-MRSA carriage among household contacts of an index patient with HA-MRSA. The frequency with which CA-MRSA strains cause disease will be assessed prospectively by determining the secondary attack rate of disease and this will be compared to that of HA-MRSA. The predominant site of CA-MRSA will also be determined by culturing both the nose and the hand. All strains will be genetically characterized by pulsed-field gel electrophoresis, multi-locus sequence typing, SCCmec typing, and lukS-PV/lukF-PV PCR to determine the clonal repertoire of CA-MRSA strains and assess relatedness among household contacts. The knowledge to be gained from this study is crucial to guide further strategies to deal with the CA-MRSA epidemic. Defining the colonization frequency among household contacts of an index case, the secondary attack rate by CA-MRSA, and the predominant site of carriage will aid in development of containment, preventative, and therapeutic management guidelines.