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Kurt B. Stevenson, MD, MPH & Dwight A. Powell, MD

Award Name Pilot Grant

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Outbreaks of Community MRSA

The Ohio State University Center for Clinical and Translational Science has awarded Kurt B. Stevenson, MD, MPH, and Dwight A. Powell, MD, with a one-year pilot grant for their research involving outbreaks of community methicillin-resistant Staphylococcus aureus (MRSA).

For several years prior coming to OSU, Stevenson served as the medical director for a community-based research group dealing with Medicare quality improvement. There, he and his team conducted a large number of studies examining antibiotic resistance in rural hospitals and ways to optimize the use of antibiotics.

Stevenson’s early work set the foundation for the interest he had in looking at MRSA in rural settings. Using the OSU Medical Center and a network of outreach hospitals that are connected to OSU, Stevenson, in a project funded by the CDC Prevention Epicenter program, has collected data on more than 1800 MRSA cases. Using the CCTS funding, he will expand this network to central Ohio hospitals, including Ohio Health, Nationwide Children’s Hospital and Mt. Carmel. In doing so, he plans to replicate his previous study using a broader approach.

Traditional methods used to study epidemiology involve examining the patients’ history and risk factors, comparing those who have an MRSA infection to those who do not, and determining which characteristics promote the development of an infection.

In addition to utilizing methods involved in traditional epidemiology, Stevenson is using three other parameters of measurement: molecular genotyping, geographic analysis, and social network analysis.

Using molecular genotyping, Stevenson has made some interesting discoveries.

“What we’re finding is there are certain genotypes of organisms that are linked with specific types of infections,” Stevenson said.

Stevenson and his colleagues are planning to partner with basic scientists to examine the organisms they believe may have predispositions to specific infection types in order to evaluate for the presence of certain virulence factors or toxin productions to account for these predispositions.

In order to conduct geographic analysis, also called “geo-coding,” information is first collected about the patient infected with a specific isolate. Then, Stevenson and his team use the address of the patient in order to geo-code them to a specific zip code or census track. Using computer software, they can create maps and determine where different genotypes are clustered in specific geographic regions. Certain types of organisms only cluster to certain communities, while others can be found spread out all over the state.

Mapping isolates with time trending allows for observations of the movement of specific genotypes between communities and regions and the appearance and disappearance of specific genotypes.

“It’s just a different way of looking at the relationships of organisms,” Stevenson said.

Using a retrospective group of organisms that had already been frozen at the OSU Medical Center for comparison purposes, Stevenson and his team have made some interesting discoveries.

“There are some genotypes that were present then that have disappeared, and then there are some genotypes that weren’t present in the retrospective group, but have appeared later,” Stevenson said.

The fourth and final method Dr. Stevenson and his colleagues are using is the observation of social networks. They look at the whereabouts of patients 90 days prior to the contraction of their infections. Using social networking software, patients are linked together and their relationships examined.

Using four methods of epidemiologic research offers a great advantage to Stevenson and his team.

“The idea is if you combine all of those things together, we get a much better picture of how the organisms evolve or how they’re inter-related or moving geographically,” Stevenson said.

The study does not use traditional recruiting methods in the classic sense of a randomized trial, said Stevenson. Instead, the study is prospective. Subjects will be recruited dependent upon whether they have a positive culture for MRSA.

The ultimate goal of the study, according to Stevenson, is to understand how the organism moves across the community and between hospitals and patients. Only then can interventions be designed to prevent the transmission of MRSA.

A past method used to monitor the transmission of MRSA is called active surveillance culturing, in which newly-admitted hospital patients are nasally swabbed immediately upon arrival looking for positive MRSA cultures. The flaw in this method is that it’s expensive and its effectiveness is debatable.

With his research, Stevenson hopes to implement a more cost-effective method that would involve strain-typing patients and focusing only on those with MRSA who have predispositions for serious infections.

The CCTS and community engagement funding will help expand the network Stevenson is working with. He and his colleagues have also written a grant in the hopes of working with a spatial statistician and bioinformatics professionals to develop mathematical models for how MRSA is being transmitted.

By Nicole Frie, Monday, August 16, 2010

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