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

描述(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年导致美国超过94,000例严重感染和18,000多例死亡。在过去的十年里，出现了新的感染MRSA的风险群体，来自欧洲和加拿大的报告已经确定了另一个紧急风险群体：接触过生猪的个人。我们小组在美国进行的初步研究表明，几乎一半被检查的养猪者都感染了MRSA。尽管在越来越多的国家发现了与牲畜相关的MRSA(LA-MRSA)，但大多数研究都使用在农场现场进行的横断面设计来检查少数工人。美国还没有对接触牲畜的工人进行大规模的队列研究，但由于MRSA的流行病学正在迅速变化，迫切需要更好地了解与耕作接触相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，包括在医疗保健环境内外收集的金黄色葡萄球菌。我们在这项应用中的目标是描述金黄色葡萄球菌在农村州的流行病学特征。我们将通过实施两项平行的前瞻性队列研究来实现这一目标，检查1)农业健康研究中登记的个人，重点是那些养猪的人；2)代表爱荷华州不同地区的基于人口的小组。虽然这些队列研究将集中在定居上，但我们将进行第三个分支机构检查该州症状感染的金黄色葡萄球菌分离株。我们的中心假设是，与牲畜工作的个人将面临职业暴露于MRSA的风险，与牲畜相关的菌株也将导致症状性感染。我们对这一项目的理由是，成功完成该项目将使我们能够在金黄色葡萄球菌在人类人口中广泛传播之前，开发针对新出现的金黄色葡萄球菌菌株的干预措施。这项拟议的研究是创新的，因为它旨在前瞻性地检查农业/农村环境中金黄色葡萄球菌的流行病学，这代表了美国40%的社区医院。在这项研究完成时，我们预计我们将确定金黄色葡萄球菌在爱荷华州农村地区的流行率和主要分子类型；描述耐药金黄色葡萄球菌菌株定居的风险因素，以及这些菌株在我们的队列中引起症状感染的频率；并确定在爱荷华州引起症状感染的MRSA菌株的分子流行病学。这些结果将为金黄色葡萄球菌在农村环境中的维持和传播提供洞察，以及可以实施的潜在机制，以防止这种出现和传播。 公共卫生相关性：在欧洲和加拿大进行的研究中，在高比例的猪和养猪工人中发现了耐甲氧西林金黄色葡萄球菌(MRSA)。最近，我们小组在对爱荷华州和伊利诺伊州的猪和农民进行的一项小型研究中发现了MRSA。我们试图确定在爱荷华州的农村地区，耐药金黄色葡萄球菌菌株的定居和感染有多普遍，并确定家畜暴露是否代表了在美国定居和感染耐药金黄色葡萄球菌的新风险因素。

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.