Scanning electron micrograph of MRSA bacteria. Credit: Janice Haney Carr/CDC

The bacterium Staphylococcus aureus can live on our skin and in our noses without causing disease. Such a condition is called bacterial colonization, to contrast it from infection in which the bacteria causes illness. When the skin is broken or when host immunity is weakened Staph. aureus can enter the blood stream or other body spaces and cause life-threatening infection. Because medical procedures frequently involve puncturing or cutting the skin, Staph. aureus accounts for more health care-associated infections than any other germ.

That would be bad enough, but one strain of Staph. aureus, called methicillin-resistant Staph. aureus (MRSA), has developed resistance to many of the antibiotics most commonly used against Staph. infections, making it particularly difficult to treat. Controlling the spread of MRSA in health-care settings has become a national priority. Many hospitals have implemented programs to remind staff to wash their hands before and after contact with patients and to identify and isolate patients colonized with MRSA. Hospital-acquired MRSA infections have actually declined in recent years, perhaps due to these efforts, but in 2011 they still affected 62,500 patients and killed more than 9,000.

ICU patients are especially vulnerable to life-threatening hospital-acquired infections, for two reasons. First, they are the sickest patients in the hospital and their immune system is frequently not working well. Second, they undergo many invasive procedures that cause potential portals of entry for infection. Some hospitals screen all patients (or all ICU patients) for MRSA by swabbing their nose. Those who test positive are then placed under contact isolation – they are moved to a private room and all staff must don gloves and a disposable gown prior to coming into contact with them. Nine states have mandated by law such MRSA screening and isolation procedures.

But is this the best way to protect hospitalized patients from MRSA infection?

Other hospitals have stepped up their MRSA efforts even further. They screen all patients for MRSA. Those who test positive are isolated and also undergo decolonization – an attempt to kill the MRSA on their skin and in their nose. This is usually done with an antibiotic gel that is placed in the nostrils and antibacterial wipes that are used to clean the patient’s skin.

Last week the New England Journal of Medicine published a very clever experiment that tried to elucidate the best way to minimize ICU-acquired MRSA infections.

Rather than randomize patients, they randomized whole hospitals. 43 hospitals were randomized to three different MRSA strategies for their ICU patients. Hospitals in the first group employed the traditional screen-and-isolate strategy. All ICU patients were screened for MRSA and those who were found to be colonized were placed under contact isolation. The second group used a screen-and-decolonize strategy. All ICU Patients were screened for MRSA and those who tested positive were placed under contact isolation but also underwent decolonization with the antibiotic nasal gel and the antibacterial skin wipes. The third group had the simplest strategy – universal decolonization. Their ICU patients did not get tested for MRSA. Instead, all the patients were decolonized with the antibiotic nasal gel and the antibacterial skin wipes.

Hospitals in the third group had the fewest MRSA infections. They also had the fewest blood-borne infections from any germ. That makes sense given that the antibacterial wipes would be expected to kill many pathogens, not just MRSA. The authors calculated that 181 patients would need to undergo decolonization to prevent one MRSA infection, and 54 patients would need to undergo decolonization to prevent one bloodstream infection from any pathogen.

Besides being the most effective, universal decolonization had another important advantage; it eliminated the need for swabbing everyone’s nose. This eliminated the expense of doing all those tests for MRSA and also eliminated the delay of waiting for the test result, since decolonization could proceed immediately.

Occasionally fortune smiles on us and the simplest solution turns out to be the most effective. The practicality of this approach makes it possible to implement it in virtually any hospital immediately.

There are some possible drawbacks. The most serious is that universal use of the antibiotic nasal gel and the antibacterial skin wipes could eventually lead to bacterial resistance to either of them. If they were to be used universally, some program to test for resistance should be also implemented. But a more immediate hurdle is that eliminating screening for MRSA would run afoul of state law in nine states.

An editorial in the same issue of NEJM states

[T]he folly of pursuing legislative mandates when evidence is lacking has been shown, and laws mandating MRSA screening should be repealed.

That is indeed a worthy goal. If this were generalized to the repeal of all “legislative mandates when evidence is lacking”, the effects of this study would be revolutionary.

Learn more:

Winning the MRSA Battle in Hospitals (Well, NY Times health blog)
New Tack in Preventing Hospital Infections (Wall Street Journal)
Disinfect All ICU Patients To Reduce ‘Superbug’ Infections (Shots, NPR health blog)
Targeted versus Universal Decolonization to Prevent ICU Infection (NEJM article, by subscription)
Screening Inpatients for MRSA — Case Closed (NEJM editorial, by subscription)