New policy strategies needed to contain MRSA spread across hospitals

Issue: May 2011

DALLAS — Better infection control strategies and policies are needed to control methicillin-resistant Staphylococcus aureus outbreaks from occurring between hospitals, according to presenter here.

“Hospitals are not isolated entities but, rather, parts of complex systems. Therefore, infectious disease control should take into account the entire system,”Sarah M. McGlone, MPH, of the Public Health Computational and Operations Research Group (PHICOR) at the University of Pittsburgh, said during a presentation. “MRSA outbreaks in a single hospital can affect many hospitals throughout a county in unexpected ways…the full effects of an outbreak can take months and even years to fully manifest throughout a county.”

For this reason, McGlone and colleagues examined how an MRSA outbreak across hospitals in Orange County, Calif., could subsequently spread to other hospitals with the use of simulated outbreaks that included a sustained single hospital outbreak, temporary single hospital outbreak, major outbreak, and a regional outbreak that reached across all hospitals in the county.

Patient movement was assessed among a total of 32 hospitals, including six long term acute care facilities and three children’s hospitals. Upon hospital admission, patients entered either a general ward or ICU; their length of stay was based on a distribution. After discharge, patients could be transferred directly to another hospital or return to the community, and may be readmitted to the same or different hospital. New MRSA cases were determined by susceptible and infectious patient data.

McGlone said that each outbreak eventually spread throughout all hospitals in the network. In one hospital, the prevalence of MRSA increased from 5% to 15%, and resulted in an average relative 2.9% increase in MRSA prevalence.

The regional simulated outbreak caused an average relative increase of 7.3%. The simulated outbreak in one hospital’s ICU led to an average relative change of 1.1% in all other Orange County hospitals. Long term acute care facilities experienced the greatest change in outbreaks (89%).

“An outbreak is potentially a regional concern; hospitals are not islands, but parts of a complex system,” McGlone said. “It’s really important for hospitals to try to connect with or communicate with each other during an outbreak, and it’s important to realize your connections with another hospital before you either make a new connection or you sever an existing connection.” – by Ashley DeNyse

Disclosures: Dr. McGlone reports no financial disclosures.

For more information:

McGlone S. #302. Presented at: SHEA 2011 Annual Scientific Meeting; April 1-4, 2011; Dallas.

Alan Tice, MD

The presentation about interhospital spread of MRSA is an exciting one which harnesses supercomputing and hence the concept of modeling of spread. Although there was a tremendous amount of work put into this study, the insight into mechanisms of transmission and actual infection or colonization should be well worthwhile. It takes a supercomputer to incorporate the variables involved in the spread of infectious diseases and unfortunately, they vary with every microbe and environment. To be able to model the spread of MRSA may be particularly helpful and provide clues as to the most important means of transmission of the bacteria and also clinical disease. If we can identify and rate the most important mechanisms, we should be able to vastly improve our methodology for control within hospitals, but even more importantly to the real source of the community-associated MRSA strains, which outnumber the hospital-associated strains 1,000 to one. The application of the incredible information analysis systems is only now becoming recognized as relevant to clinical care, but the time is ripe for it and it should improve dramatically with the transition of classic bench microbiology to molecular biology with almost real-time identification of pathogens but also their anti-microbial resistance and virulence factors. The ability to also combine the data from all the computers proliferating in microbiology labs around the world offers remarkable potential to provide alerts and quick responses to any outbreaks — and with far more insight than we have ever had before.

– Alan Tice, MD
Infectious Disease News Editorial Board member

Disclosure: Dr. Tice reports no relevant financial disclosures.

With few new antibiotics in the pipeline, we need to conserve the antibiotics that we have. This important research shows that there is much room for improvement in our antibiotic stewardship efforts.

– Marin L. Schweizer, PhD
University of Iowa, Carver College of Medicine

Disclosure: Dr. Schweizer reports no relevant financial disclosures.

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