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Study finds a decline in MRSA in the ICU

Specific causes remain unknown, but CDC guidelines seem to be working

On an all-too-regular basis, newspaper headlines depict grim trends related to MRSA, both in the hospital and the community. Health officials have been left scrambling to mitigate the pathogen’s drug resistance, and infection preventionists (IPs) are working hard to keep it from entering their hospitals.

But a recent study published in the February 18 Journal of the American Medical Association (JAMA) offers a glimmer of hope in the fight against this antibiotic-resistant infection.

Researchers at the Centers for Disease Control and Prevention (CDC) examined trends regarding the incidence of MRSA in central line–associated bloodstream infections (CLABSI) in U.S. ICUs. Data reported to the CDC through the National Nosocomial Infections Surveillance system from 1997 to 2004 were used in conjunction with data from the National Healthcare Safety Network (NHSN) that were phased in by the CDC in 2005.

After analyzing data over the 10-year period, researchers found that although MRSA CLABSI incidence from 1997 to 2001 increased in some ICU settings, from 2001 to 2007, MRSA rates declined in all ICU types except pediatric units. Overall, the CLABSI incidence decreased 49.6% over the 10-year span.

Why ICUs?

The study focused on a particular set of parameters. It concentrated on data related to MRSA bloodstream infections, specifically at ICUs.

Deron C. Burton, MD, JD, MPH, lieutenant commander at the U.S. Public Health Service assigned to the CDC, and lead researcher of the study, says the reason for studying ICUs specifically was mostly a result of very limited parameters offered by the data.

“The surveillance systems that we have been using to gather this data have traditionally been focused on the ICU setting,” Burton says. “Even though we have non-ICU settings included in the most current version of the surveillance system, in order to have continuity of reporting over the last 10 years of surveillance data, we actually needed to limit it to the ICUs.”

Shortly after the study was published, APIC CEO Kathy L. Warye released a statement about the report’s results.

“This is encouraging news for patients and the healthcare community,” Warye said in the statement. “While central line–associated bloodstream infections caused by MRSA represent only a small fraction of the overall number of MRSA infections, this analysis demonstrates that healthcare-associated infections [HAI] can be prevented in a very vulnerable group of patients when institutions consistently implement evidence-based prevention strategies.”

Despite the limitations of the study, the ICU setting serves as a good gauge in evaluating current prevention measures, Burton says.

“We also think that it’s important to look in the ICU setting for what’s going on with MRSA in particular, given the elevated risk of the patients in the ICU,” Burton says. “So even though, as you know, it’s a problem in other environments in the healthcare setting, given the high risk of this particular population, we think it’s an important area that has seen success in combating this problem.”

Nevertheless, Burton emphasizes that the results of the analysis reported in JAMA cannot be generalized to other kinds of MRSA HAIs or to MRSA infections in other hospital areas.

Explaining the decrease

Although the study served as a positive note for IPs, the limitations of the study were such that it could not specifically cite any measures that had a direct effect on the decrease of infections. Because the reporting system did not include those types of data, researchers were forced to evaluate raw numbers rather than point to a specific procedure or method.

“We are really left with this analysis saying there are a lot of things going on, and in the aggregate it seems like these things are having an effect,” Burton says. “We can’t rule out, obviously, that these are secular trends unrelated to prevention efforts, but it seems very likely these are a reflection of successes with prevention efforts. We just can’t say specifically which ones.”

The infection prevention guidelines released by the CDC, specifically Guidelines for the Prevention of Intravascular Catheter–Related Infections, CDC Guideline for Hand Hygiene in Healthcare Settings, and SHEA Guideline for Preventing Nosocomial Transmission of Multidrug-Resistant Strains of Staphylococcus aureus and Enterococcus, seem to have a positive effect on prevention measures, since many facilities have begun using these recommendations. Vague as the explanation may be, healthcare facilities seem to be headed in the right direction, although you won’t find any specific answers without data linking procedures and practices to outcomes.

“Certainly, having more data will help us get a better and more precise handle on what is happening across the country [and] will allow us to do more refined analysis looking at some types of hospital by particular characteristic,” Burton says. “It won’t directly allow us to hone in on specific interventions unless we start getting additional data elements that we don’t currently collect reported to us about the interventions being used by facilities over time.”

The study weeds out two methods that have been widely discussed, particularly at the state legislative level, Burton says.

“We don’t think, though, that the declines can be fully attributed to widespread use of screening or public reporting laws, because those things did not come into use until rather late in our surveillance period,” says Burton.

The need for more research

As is common with many medical studies, this one concludes with a call for further studies to narrow down exactly what procedures have been effective and where infection prevention can continue to succeed, particularly in other areas of the industry.

In her statement, Warye also addressed this issue, noting that further studies will help translate best practices to other areas of the hospital.

“More research is also needed to determine if approaches that are successful in the ICU can be replicated elsewhere in the hospital, where the majority of MRSA resides,” Warye said.

“Hospitals that are successful in reducing HAIs are using a multifaceted approach, employing a group of interventions to address MRSA and other dangerous pathogens,” Burton says.

Future studies also need to be more concentrated and specific to garner explicit reasons for the decline in MRSA incidence.

To do that, studies will probably be limited to researching IC measures on a smaller scale, Burton says.

“I think those studies were certainly being talked about, considered, and pursued already, and I think there is no reason to think they won’t continue to have interest after this study,” Burton says.

Percent MRSA vs. MRSA incidence

In addition to rewriting the common misconception that MRSA is a growing problem within the ICU setting, researchers also uncovered a subtle, yet significant bit of information related to the way MRSA cases are measured.

In the study’s conclusion, the authors noted that there has been a reliance on percent MRSA in measuring trends. This measurement may in fact be misleading, according to the researchers.

Percent MRSA measures the likelihood that if a patient contracts a staph infection, the infection will be MRSA, according to Deron C. Burton, MD, JD, MPH, lieutenant commander at the U.S. Public Health Service assigned to the CDC, and lead researcher of the study. MRSA incidence, on the other hand, measures absolute risk, or the chance that a patient will contract a MRSA bloodstream infection if a central line is inserted.

“Put another way, if you have a given number of ICU patients that have central lines used in them for a given period of time, how many infections are you likely to see, or would you expect to see, caused by MRSA?” says Burton.

During the study, researchers found several discrepancies between these two measurements. Most notably, over the 10-year period percent MRSA increased 25% whereas MRSA incidence decreased 50%.

The researchers suggested that caution should be exercised when interpreting MRSA data, and that reporting percent MRSA without providing MRSA incidence could be misleading.