Issue: October 2011
October 01, 2011
2 min read

Children colonized with MRSA prone to full-blown infection

Milstone AM. Clin Infect Dis. 2011;doi:10.1093/cid/cir547.

Issue: October 2011
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Children who are colonized but not sick with methicillin-resistant Staphylococcus aureus are at an increased risk for developing full-blown infections, according to a study published online.

Aaron M. Milstone, MD, of Johns Hopkins University, and colleagues examined data on 3,140 children admitted to the Johns Hopkins pediatric ICU between 2007 and 2010. Routine screening revealed that 153 children arrived at the hospital already colonized with MRSA, and when the researchers compared these patients with noncarriers, they reported that carrier patients were nearly six times more likely to develop invasive MRSA infections after discharge. These patients were also eight times more likely to develop them while still hospitalized, according to the study results.

Fifteen of the children came to the hospital without MRSA but acquired the bacterium while in the pediatric ICU. The finding, the researchers said, calls attention to the risk for MRSA spread among vulnerable patients.

The researchers said black patients and patients without private health insurance were more likely to get a subsequent infection (P<.01 and P=.03, respectively).

“Hospitalized children colonized with MRSA have a very real risk for invasive infections, both while in the hospital and once they leave, so mitigating this risk is a serious priority,” Milstone said in a press release about the study. “We need standardized protocols on ways to protect MRSA carriers from developing invasive infections while also minimizing its spread to others.”

Until protocols are developed, Milstone urged health care providers to wash their hands frequently and to preemptively decolonize carriers by applying a topical antibiotic in the nostrils and bathing them with antiseptic solution.

The study researchers said preemptive treatment may be especially beneficial in hospitalized children because their immune systems are typically weakened by illness, making them far more vulnerable to invasive disease than healthy MRSA carriers.

Disclosures: The research was funded by the NIH. One of the study researchers sits on the advisory board for Hospira, a pharmaceutical company and manufacturer of drug-delivery devices. This relationship is managed by The Johns Hopkins University in accordance with its conflict-of-interest policies.


C. Buddy Creech
C. Buddy

This manuscript by Aaron Milstone and his colleagues at Johns Hopkins underscores the importance of carefully defining the clinical and molecular epidemiology of staphylococcal colonization in children. The study, demonstrating that children admitted to the PICU with MRSA nasal colonization were significantly more likely to develop MRSA infections, is a sobering reminder of the potential effects of this commensal organism.

While the magnitude of the impact could be debated (due to sample size, definition of tracheitis, or failure to capture all subsequent infections), there is little doubt that the authors' central conclusion is sound. MRSA colonization is a risk factor for subsequent disease, particularly when colonization is due to USA300 CA-MRSA. This is the real crux of the argument. If the American microbiologist Theobald Smith was right, then "disease is an accident that occurs during the development of the parasitic state." It is entirely plausible, and indeed likely, that certain strains of S. aureus are more "accident-prone" than others. Milstone and colleagues have shown this nicely, as the majority of colonization strains and disease strains were found to be CA-MRSA. This supports the notion that knowledge of staphylococcal colonization alone (yes/no) may be insufficient to guide prevention; rather, knowledge of the molecular characteristics of the organism are necessary to devise an effective prevention strategy.

What then should be done? It is not clear whether the indiscriminate decolonization of all MRSA carriers should be performed. The data remain mixed on this issue and complications such as mupirocin resistance and strain replacement are to be expected. Nevertheless, Milstone et al provide compelling data that if we are to "first, do no harm," then aggressive disease surveillance, at the very least, should be initiated on those found to be carriers of this increasingly complex pathogen.

C. Buddy Creech, MD, MPH
Infectious Diseases in Children Editorial Board member

Disclosure: Dr. Creech reports no relevant financial disclosures.

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