Optimizing Detection of MRSA Carriage

描述（由申请人提供）：金黄色葡萄球菌是医疗保健相关感染的主要原因。2003年，美国医院估计有40万例金黄色葡萄球菌感染病例。大约60%的金黄色葡萄球菌医院感染是由耐甲氧西林金黄色葡萄球菌（MRSA）引起的。据估计，MRSA感染每年导致近19,000名住院美国患者死亡。虽然金黄色葡萄球菌已知定殖于各种解剖部位，但其主要栖息地是前鼻孔的上皮。因此，使用鼻拭子培养对MRSA进行主动筛查，然后对携带者进行接触者隔离，是美国医院广泛采用的感染控制策略，以防止该细菌在患者之间交叉传播。社区相关性MRSA （CA-MRSA）菌株的出现，由于其独特的遗传特征和引起皮肤和软组织感染的倾向，正在迅速改变MRSA的流行病学。CA-MRSA菌株，以脉冲场型（PFT） USA300克隆为代表，可能在体表具有不同于医疗相关MRSA （HA-MRSA）菌株的定植模式。随着CA-MRSA流行的进展，CA-MRSA菌株日益成为医疗保健相关感染的常见原因。在我们的初步研究中，我们发现相当一部分被MRSA定植的患者是在皮肤上定植的，但不一定是在鼻腔上。此外，对于一些患者，我们可以使用海绵（可以对大面积皮肤进行取样）而不是拭子来恢复MRSA。本研究的具体目的是：(1)阐明MRSA在急性护理医院患者中的定植模式，并研究海绵筛查方法的敏感性；(2)通过确定不同解剖部位定植的菌株的基因型，确定CA-和HA-MRSA菌株定植模式的差异。本试验的主要目的是开发一种耐甲氧西林金黄色葡萄球菌定植的敏感筛选方法。这种方法将成为研究MRSA定植动态和评估感染控制措施（如携带者的非定植）有效性的有用工具。

DESCRIPTION (provided by applicant): Staphylococcus aureus is a major cause of healthcare-associated infection. An estimated 400,000 cases of S. aureus infection occurred in US hospitals in 2003. Approximately 60% of S. aureus hospital infections are caused by methicillin-resistant S. aureus (MRSA). It is estimated that MRSA infections are responsible for the death of nearly 19,000 hospitalized American patients annually. While S. aureus is known to colonize various anatomic sites, its primary habitat is the epithelium of the anterior nares. Therefore, active screening for MRSA using nasal swab culture followed by contact isolation of carriers is a widely practiced infection control strategy in US hospitals to prevent cross-transmission of this organism between patients. The advent of community-associated MRSA (CA-MRSA) strains, which are defined by distinct genetic traits and tendency to cause skin and soft tissue infection, is rapidly changing the epidemiology of MRSA. CA-MRSA strains, represented by the pulsed-field type (PFT) USA300 clone, may have a colonization pattern on the body surface that differs from healthcare- associated MRSA (HA-MRSA) strains. As the CA-MRSA epidemic progresses, CA-MRSA strains are increasingly becoming a common cause of healthcare-associated infections. In our preliminary study, we found that a substantial portion of patients who are colonized with MRSA are colonized on the skin, but not necessarily the nares. In addition, for some patients, we were able to recover MRSA using a sponge (which can sample a large area of the skin), but not swabs. The specific aims addressed in this proposal are (1) to elucidate the colonization patterns of MRSA among patients in an acute care hospital and investigate the sensitivity of sponge-based screening method, and (2) to identify the difference in colonization patterns of CA- and HA-MRSA strains by determining the genotypes of the strains colonizing various anatomic sites. The main objective of this pilot is to develop a sensitive screening method for MRSA colonization. Such a method will then serve as a useful tool in studying the dynamics of MRSA colonization and evaluating the efficacy of infection control practices such as decolonization of carriers. PUBLIC HEALTH RELEVANCE: Methicillin-resistant S. aureus (MRSA) is a major cause of healthcare-associated infection in the United States. In many hospitals, whether a patient carries MRSA or not is determined by culturing of the nose. The proposed study aims to identify whether there are anatomic sites that are more sensitive in detecting MRSA than the nose, and whether the use of sponge enhances detection of MRSA.