Epidemiology of rural MRSA: is livestock contact a risk factor?

描述（由申请人提供）：最近的一份报告记录了耐甲氧西林金黄色葡萄球菌（MRSA）的临床影响，表明MRSA在2005年在美国造成了超过94,000例严重感染和超过18,000例死亡。在过去的十年中，出现了新的有感染MRSA风险的群体，来自欧洲和加拿大的报告已经确定了另一个新出现的风险群体：与活猪接触的个人。我们小组在美国进行的初步研究表明，接受检查的养猪工人中几乎有一半被MRSA定植。尽管在越来越多的国家发现了与牲畜相关的MRSA (LA-MRSA)，但大多数研究都是在农场现场使用横断面设计检查了少数工人。在美国尚未对接触牲畜的工人进行大规模队列研究，但由于MRSA的流行病学正在迅速变化，因此迫切需要更好地了解与农场接触有关的新型金黄色葡萄球菌分离株的流行病学。这些知识对于评估传染病风险和确定预防措施将是非常宝贵的。我们的长期目标是更好地了解农村社区金黄色葡萄球菌的流行病学，包括在医疗机构内外收集的金黄色葡萄球菌。我们在这个应用程序的目的是表征金黄色葡萄球菌的流行病学在农村状态。我们将通过开展两项平行的前瞻性队列研究来实现这一目标，1)对农业健康研究中登记的个体进行检查，重点是养猪的个体；2)一个以人口为基础的群体，代表爱荷华州的一个横截面。虽然这些队列研究将侧重于定植，但我们将进行第三组研究，检查该州症状感染中的金黄色葡萄球菌分离株。我们的中心假设是，与牲畜一起工作的个人将面临职业暴露于MRSA的风险，并且与牲畜相关的菌株也将引起症状性感染。我们这个项目的基本原理是，成功完成将允许开发针对新出现的金黄色葡萄球菌菌株的干预措施，在它们在人群中广泛传播之前。拟议的研究具有创新性，因为它旨在前瞻性地检查金黄色葡萄球菌在农业/农村环境中的流行病学，这代表了美国40%的社区医院。在这项研究完成后，我们期望我们将确定爱荷华州农村金黄色葡萄球菌的患病率和优势分子类型；描述耐抗生素金黄色葡萄球菌菌株定植的危险因素，以及这些因素在我们的队列中引起症状性感染的频率；并确定了在爱荷华州引起症状感染的MRSA菌株的分子流行病学。这些结果将有助于深入了解金黄色葡萄球菌在农村环境中的维持和传播，以及预防其出现和传播的潜在机制。

DESCRIPTION (provided by applicant): A recent report has documented the clinical impact of methicillin-resistant Staphylococcus aureus (MRSA), suggesting that MRSA caused over 94,000 serious infections and more than 18,000 deaths in the U.S. in 2005. In the past decade, new groups at risk of acquiring MRSA have emerged, and reports from Europe and Canada have identified another emergent risk group: individuals in contact with live swine. Pilot studies in the U.S. carried out by our group have shown that almost half of the swine workers examined were colonized with MRSA. Though livestock-associated MRSA (LA-MRSA) have been found in an increasing number of countries, most studies have examined a small number of workers using a cross- sectional design conducted on the farm site. A large cohort study of livestock-exposed workers has not been conducted in the U.S., but as the epidemiology of MRSA is rapidly changing, there is a critical need to better understand the epidemiology of novel S. aureus isolates associated with farming exposures. Such knowledge would be invaluable in assessing infectious disease risks and determining preventative measures. Our long-term goal is to better understand the epidemiology of S. aureus in the rural community, including S. aureus collected both inside and outside of the healthcare setting. Our objective in this application is to characterize the epidemiology of S. aureus in a rural state. We will achieve this goal by carrying out two parallel prospective cohort studies, examining 1) individuals enrolled in the Agricultural Health Study, focusing on those who raise swine; 2) a population-based group representing a cross-section of Iowans. While these cohort studies will focus on colonization, we will carry out a third arm examining S.aureus isolates from symptomatic infections in the state. Our central hypothesis is that individuals working with livestock will be at risk of occupational exposure to MRSA, and that livestock-associated strains will also be causing symptomatic infections. Our rationale for this project is that successful completion will allow for the development of interventions targeting emerging S. aureus strains prior to their widespread dissemination in the human population. The proposed research is innovative because it is designed to prospectively examine the epidemiology of S. aureus in an agricultural/rural setting, which represents 40% of the community hospitals in the U.S. At the completion of this research, it is our expectation that we will have established the prevalence and dominant molecular types of S. aureus in rural Iowans; delineated risk factors for colonization with antibiotic-resistant S. aureus strains, and the frequency with which these cause symptomatic infection in our cohorts; and determined the molecular epidemiology of MRSA strains causing symptomatic infections in Iowa. These results will provide insight into the maintenance and spread of S. aureus in the rural environment, as well as potential mechanisms that could be implemented to prevent such emergence and spread. PUBLIC HEALTH RELEVANCE: Methicilin-resistant Staphylococcus aureus (MRSA) has been found in a high proportion of swine and swine workers in studies carried out in Europe and Canada. Recently, our group has identified MRSA in a small study of swine and farmers in Iowa and Illinois. We seek to determine how common colonization and infection with strains of antibiotic-resistant S. aureus are in rural Iowans, and to determine if livestock exposure represents a new risk factor for colonization and infection with antibiotic-resistant S. aureus in the United States.