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Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus MRSA
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Methicillin resistance in Staphylococcus aureus infections among patients colonized with methicillin-susceptible

N K Shrestha1, T G Fraser1, S M Gordon1

  • 1Department of Infectious Diseases, Cleveland Clinic, Cleveland, OH, USA.

Clinical Microbiology and Infection : the Official Publication of the European Society of Clinical Microbiology and Infectious Diseases
|April 13, 2018
PubMed
Abstract

Insights

Patients carrying methicillin-susceptible Staphylococcus aureus (MSSA) are significantly less likely to develop methicillin-resistant Staphylococcus aureus (MRSA) infections. This study found MSSA carriers had 125 times lower odds of MRSA infection compared to MRSA carriers.

Area of Science:

  • Infectious Diseases
  • Clinical Microbiology
  • Epidemiology

Background:

  • Methicillin-susceptible Staphylococcus aureus (MSSA) colonization is common.
  • Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant healthcare threat.
  • Understanding the relationship between MSSA and MRSA colonization and infection is crucial for infection control.

Purpose of the Study:

  • To investigate the association between Staphylococcus aureus (SA) carrier status (MRSA, MSSA, or non-carrier) and the likelihood of developing an MRSA infection.
  • To quantify the difference in MRSA infection odds among different SA carrier groups.

Main Methods:

  • Retrospective analysis of adult hospitalizations at Cleveland Clinic Health System (2008-2015).
  • Identification of patients tested for SA colonization and subsequent SA infection.
  • Classification of carrier status based on the first nasal SA test (MRSA, MSSA, or non-carrier).
  • Statistical analysis to compare MRSA infection odds across carrier groups, controlling for covariates.

Main Results:

  • Of 1999 included patients, 30% were MRSA carriers, 26% MSSA carriers, and 44% non-carriers.
  • Among patients with SA infection, 92% of MRSA carriers developed MRSA infections.
  • In contrast, only 8% of MSSA carriers and 49% of non-carriers developed MRSA infections.
  • MSSA carriers had significantly lower odds of MRSA infection (OR 0.008) compared to MRSA carriers.

Conclusions:

  • MSSA colonization is strongly protective against the development of MRSA infections in hospitalized patients.
  • The odds of an SA infection being MRSA are dramatically reduced in MSSA carriers compared to MRSA carriers (125-fold difference).
  • These findings have implications for infection prevention strategies and risk stratification in healthcare settings.
Keywords:
MRSAMSSAStaphylococcus aureusStaphylococcus aureus carrierStaphylococcus aureus colonization

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