Spread of Community-Acquired MRSA Among Household Contacts

描述（由申请方提供）：流行性社区获得性耐甲氧西林金黄色葡萄球菌（MRSA）是一种新发传染病，发生于既往健康的儿童和成人，无MRSA感染风险因素。这些新的社区获得性MRSA（CA-MRSA）菌株与医院获得性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，引起与社区获得性甲氧西林敏感的S.金黄色葡萄球菌（CA-MSSA），并含有编码溶细胞毒素Panton-Valentine杀白细胞素的基因。当对这些CA-MRSA菌株中负责抗生素敏感性模式的遗传元件进行表征时，现在称为“葡萄球菌染色体盒mec”IV型或SCCmec IV型，人们意识到发生了一种独特的现象，不涉及HA-MRSA向社区的传播。由于CA-MRSA引起的皮肤和软组织感染、坏死性肺炎和脓毒症综合征的爆发报告频率越来越高。我们正在寻求关于如何防止这些菌株传播以及如何治疗受感染和殖民化个体的关键信息。CA-MRSA在家庭成员中定植的自然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疾病指示病例的家庭接触者进行CA-MRSA定殖检测。家庭接触者中CA-MRSA携带率将与HA-MRSA指示患者的家庭接触者中HA-MRSA携带率进行比较。将通过确定疾病的二次发作率来前瞻性评估CA-MRSA菌株引起疾病的频率，并将其与HA-MRSA进行比较。CA-MRSA的主要部位也将通过培养鼻子和手来确定。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 PCR对所有菌株进行遗传表征，以确定CA-MRSA菌株的克隆库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流行病的进一步策略至关重要。确定家庭接触者的指标病例的定植频率、CA-MRSA的继发性攻击率和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.