It Must Have Been the Noses: Evaluating the Evidence for Decolonization

Author: Marc-Oliver Wright, MT(ASCP), MS, CIC, FAPIC

Historical milestones

In the summer of 1980, Bryan and colleagues at Richland Memorial Hospital and the University of South Carolina reported the results of a survey of 113 of the United States’ largest hospitals¹. They had asked infection control programs how they would handle a theoretical outbreak of Staphylococcus species infections in their nursery or neonatal intensive care unit. Specifically, they asked if they would screen healthcare workers for Staphylococcus nares colonization (Yes= 70.8%) and if positive would they prescribe antibiotic ointment for their staff while awaiting bacteriophage typing results (Yes=39.8%). ¹

Four years later, Bartzokas and colleagues at the Royal Liverpool Hospital described stopping an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) through their vascular surgery unit by regular whole body bathing with a 2% triclosan which the authors suggested “should be more effective than treatment of selected carriage sites only.” ²

By 1996, John Boyce warned us to proceed with caution-noting that since the 1940s more than 50 different Staphylococcus decolonization regimens had been evaluated and that the majority were either not effective, fraught with side effects and/or lead to the development of resistance against agents used.  Twenty-five years later the debate over ideal protocols is ongoing. ³

Decolonization Beyond the Nares

Leonard Mermel described in detail the various anatomical sites and combinations thereof where MRSA could be recovered from colonized individuals. While the nares predominated all other sites (48/53), most (40/53) patients also had the organism recovered from the groin, axilla or perineum. ⁴ A larger study of 3,464 patients including blood donors, dental patients, healthcare workers and hospitalized patients revealed that only 32% of Staphylococcus aureus carriers were exclusively colonized in the nares. ⁵

Even if colonization starts in the nares, it surely doesn’t stay there. In a 2015 study, researchers showed that medical students touched their face on average 23 times each hour, nearly half of which involved mucous membranes, a third of which involved the nose. ⁶   Bacterial migration across various anatomical sites is an ongoing and an unsurprising phenomenon.

Evaluating the Evidence

The validity of any study’s results is contingent on a solid foundation of principles described in the “Methods” section and the reader should review these carefully- fallible methods can net unreliable results. In recent years, there have been a handful of studies assessing the efficacy and duration of S. aureus decolonization. A key consideration in reviewing these studies is their method of decolonization. Is their use of a nasal decolonizing agent in alignment with manufacturer’s instructions? Did their regimen include concurrent chlorhexidine (or similar) bathing (at a minimum) or antiseptic oral rinse? For example, in a recent randomized controlled clinical trial, researchers attempted to assess the degree of antiseptic suppression of MRSA via antiseptic nares decolonization alone despite the fact that 90% of the study participants were colonized at other anatomical locations in addition to the nares.⁷

If Staphylococcus aureus colonization is known to be concurrent in multiple anatomical locations and their migration between locations is aided by human behavior, then studies that assess decolonization protocols cannot be limited to the nares alone.

About Face

There are many unresolved questions regarding decolonization. Which patients? How best to prevent pathogen resistance? Do we test and treat? While the perfect protocol to achieve decolonization may still be unresolved, looking beyond the end of our nose is critical when attempting to answer these questions.