How biofilms contribute to nosocomial infections

Not Staph aureus forming a biofilm, from Science Daily

Via Science Daily, an article to demonstrate the complex interaction between the host, the pathogen, and an implanted medical device. The study, done by researchers at The Ohio State University and Duke University Medical Center, and published recently in the Proceedings of the National Academy of Sciences, examined the genetics of Staphylococcus aureus isolated from implanted cardiac devices such as defibrillators and artificial heart valves. Approximately 40,000 of the 1 million patients who receive these devices annually must have them removed and replaced with added medical costs of up to $1 billion annually, due to an acquired nosocomial infection. This research examines the genetic basis of the organisms leading to the complications. 

What was found is actually very interesting.  These nosocomial diseases (acquired during the course of a hospitalization, but not directly related to the reason for the procedure) develop from the patient’s own microbial flora; that is microorganisms that are part of the bacteria found in the absence of disease. Prior to the surgery, the organism exists in a commensal relationship with the host, and doesn’t lead to any significant signs or symptoms. The problems arise due to the implantation of the specific devices; the metal and plastic surfaces on the devices are biologically inert and so do not offer any transplant rejection issues that would be a problem with donor tissue, but these do present a fantastic surface for microorganisms to adhere to, which may initiate the formation of a biofilm inside the body. Once a biofilm has formed, the implanted medical device must be removed and replaced, as antibiotic treatments are unable to eliminate the pathogen from the body.

The researchers identified several S. aureus genes found on the surface of the cells that interacted with human blood proteins that coat the implanted medical devices once implanted. These proteins act as the first point of attachment for the formation of the biofilm, but interestingly not all S. aureus isolates have these special proteins. Once the specificity of the interaction can be mapped, the hope is that targeted drugs could be developed to prevent the interaction from occurring in the first place, and preventing the biofilm from forming.

The report is one of the first to describe why some patients have complications with their implanted devices and others do not. The issues may not be due to the patient themselves, or something about the device, but instead with the normal microbiota living on them prior to the surgery. If the ‘wrong’ organisms are present to begin with, the patient may have a more significant likelihood of developing a nosocomial infection, and subsequent need later surgery as treatment. Understanding of how the infection process originates offers the promising possibility of blocking the complicating infection in the first place.


About ycpmicro

My name is David Singleton, and I am an Associate Professor of Microbiology at York College of Pennsylvania. My main course is BIO230, a course taken by allied-health students at YCP. Views on this site are my own.

Posted on October 28, 2011, in Microbes in the News, Wash your hands! and tagged , , , . Bookmark the permalink. Comments Off on How biofilms contribute to nosocomial infections.

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