MRSA screening may benefit H1N1 patients

Feb. 1, 2010
In the midst of the H1N1 pandemic, do not forget about methicillin-resistant
Staphyloccoccus aureus
(MRSA)! As we enter 2010 and look back at 2009, it was an busy year for those in infectious diseases and microbiology with the arrival of an unexpected visitor, the pandemic influenza A/H1N1.

The Centers for Disease Control and Prevention
(CDC) recently estimated that influenza A/H1N1 infected one in six
people in the United States during 2009, with estimates of nearly 10,000
The CDC estimates there were between 34 million and 67 million cases of
influenza A/H1N1 in the United States between April and November 2009,
and between 154,000 and 303,000 H1N1-related hospitalizations.1
As a result, a tremendous amount of resources in laboratories and
healthcare facilities, as well as state and federal government agencies,
was directed toward implementing the most rapid and accurate methods of
testing patients for influenza A/H1N1 and the use of antiviral

Just as with the influenza pandemic of 1918 and
more recently in the early 2000s,2 all of the
respiratory-related deaths, have not been due to primary influenza
A/H1N1, as secondary pneumonias due to Streptococcus pneumoniae,
Staphylococcus aureus
, and MRSA have been described.3
These secondary bacterial pneumonias, either acquired in the community
or in a healthcare facility, including ventilator-associated pneumonia,
or VAP, continue to be a challenge for the medical community, both in
recognition of their potential presence and in determination of
appropriate treatment decisions for the patients with acute respiratory
disease suggestive of influenza A/H1N1 who do not respond to antiviral

Prior to the influenza A/H1N1 pandemic of 2009,
the healthcare infection surveillance system of the CDC, the National
Health and Safety Network, or NHSN, reported that MRSA accounted for
56.2% of all device-related infections and 49.2% of all surgical-site
infections, respectively, due to S aureus detected among their
member hospitals for 2006 and 2007.4 Thus, as we await
reports of healthcare-associated infections (HAIs) that have occurred
during the H1N1 pandemic, clinicians should be vigilant about the
possibility of MRSA as a complication of hospitalized patients,
including those with influenza A/H1N1.

In a landmark study in the United States by
Robicsek and colleagues, universal admission testing of and eradication
therapy for MRSA carriers decreased the subsequent numbers of HAIs due
to MRSA.5
Subsequently, additional healthcare facilities, such as the Pitt County
Memorial Hospital, the teaching hospital of The Brody School of
Medicine, implemented programs of “Search and Destroy,” with similar
positive decreases in healthcare associated-MRSA (HA-MRSA) infections.6

Earlier studies of the use of rapid, PCR-based
MRSA testing had suggested a 75% correlation of positive nasal MRSA
result with clinical respiratory disease due to MRSA among hospitalized
patients.7 Thus, as we are in middle of the usual influenza
season, testing all admissions for MRSA via nasal swabs and rapid
molecular testing may be of potential benefit in detecting those
carriers of MRSA who may or may not have concurrent respiratory disease
due to MRSA.

… be vigilant about the possibility of MRSA as a complication of
hospitalized patients, including those with influenza A/H1N1.

In summary, MRSA has been one of the leading, if
not the leading, bacterial agent of HAIs during the past decade. If the
Infection Control Risk Assessment at your hospital identifies HA-MRSA
infections as a top priority, there are increasing numbers of rapid,
commercial assays available to test and detect carriers of MRSA within
minutes to hours. Therefore, do not forget about the detection and
prevention of HAIs in this time of influenza A/H1N1, and continue to be
vigilant about the potential appearance of a third wave of influenza
A/H1N1 in communities across the United States.

Keith M. Ramsey, MD, is a professor of Medicine
at The Brody School of Medicine at East Carolina University and medical
director of Infection Control at Pitt County Memorial Hospital and
University Health systems of Eastern Carolina in Greenville, NC.


  1. Centers for Disease Control and Prevention. Estimates of 2009
    H1N1 Influenza Cases, Hospitalizations and Deaths in the United
    States, April-November 14, 2009.
    . Accessed
    January 5, 2010.
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    community-acquired pneumonia due to Staphylococcus aureus,
    2003-04 Influenza Season. EID. 2006;12(6):894-899.
  3. Centers for Disease Control and Prevention. Bacterial
    Coinfections in Lung Tissue Specimens from Fatal Cases of 2009
    Pandemic Influenza A (H1N1) — United States, May-August 2009.
    MMWR. 2009;58(38);1071-1074.
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    MF. Active Surveillance Screening and Eradication of Methicillin
    Resistant Staphylococcus aureus (MRSA) carriage decreases
    Surgical Site Infections due to MRSA. J Am Coll Surg.
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