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Development and Assessment of Intracellular Infection Models for Staphylococcus aureus
Published on: January 17, 2025
Progression from new methicillin-resistant Staphylococcus aureus colonisation to infection: an observational study in
Michelle N D Balm, Andrew A Lover, Sharon Salmon
1Infection Control Team, National University Hospital, Singapore, Singapore. mdcfda@nus.edu.sg.
Background:
Patients newly colonised with methicillin-resistant Staphylococcus aureus (MRSA) are at higher risk of clinical MRSA infection. At present, there are limited data on the duration or magnitude of this risk in a hospital population with a known time of MRSA acquisition.
Methods:
A retrospective cohort study of 909 adult patients known to have newly identified MRSA colonisation during admission to National University Hospital, Singapore between 1 July 2007 and 30 June 2011 was undertaken. Patients were excluded if they had history of previous MRSA colonisation or infection, or if they had been a hospital inpatient in the preceding 12 months. Data were collected on the development of MRSA infection requiring hospitalisation up to 30 June 2012.
Results:
Of 840 patients newly colonised with MRSA as identified on active surveillance and not clinical specimens, 546 were men (65.0%) and the median age was 65 years (range 18-103 years). Median follow up was 24 months (range 0 -64 months, 85.1% followed >6 months). Clinical infection occurred in 121 patients (14.4%) with median time to infection of 22 days (95% CI 14-31). Overall 71.9% (87/121) of infected patients developed infection within 60 days of the date MRSA colonisation was detected. However, 17/121 patients (14.0%) developed clinical infection more than six months after documented MRSA acquisition. The most common sites of clinical infection were skin and soft tissue (49/121, 40.5%, 95% CI 31.7-49.8), respiratory tract (37/121, 30.6%, 95% CI 22.5-39.6) and bone and joint infections (14/121, 11.6%, 95% CI 6.5-18.7). Thirteen patients (13/121, 10.7%, 95% CI 5.8-17.7) had bacteraemias, of which six (5.0% 95% CI 1.8-10.5) were primary and seven (5.7%, 95% CI 2.3-11.6) were secondary to infection at other sites. Crude mortality at 30 days and six months was higher in patients with MRSA infection than colonisation alone (aOR 5.49, 95% CI 2.75-10.95, p<0.001 and aOR 2.94, 95% CI 1.78-4.85, p<0.001 respectively).
Conclusion:
Risk of clinical infection is highest soon after MRSA acquisition. Prevention of MRSA acquisition in hospital will have significant impact on morbidity and mortality for patients.
Insights
Newly acquired methicillin-resistant Staphylococcus aureus (MRSA) significantly increases clinical infection risk, particularly within 60 days. Preventing MRSA acquisition in hospitals can reduce patient morbidity and mortality.
Area of Science:
- Infectious Diseases
- Hospital Epidemiology
- Clinical Microbiology
Background:
- Patients newly colonized with methicillin-resistant Staphylococcus aureus (MRSA) face an elevated risk of developing clinical MRSA infections.
- Limited data exists on the precise duration and magnitude of this risk in hospitalized patients with known MRSA acquisition times.
Purpose of the Study:
- To investigate the risk and timing of clinical MRSA infection following new MRSA colonization in hospitalized adults.
- To quantify the association between MRSA colonization and subsequent MRSA infection, morbidity, and mortality.
Main Methods:
- A retrospective cohort study included 840 adult patients newly colonized with MRSA during hospitalization at National University Hospital, Singapore (2007-2011).
- Exclusion criteria included prior MRSA history or recent hospitalizations.
- Data on the development of MRSA infection requiring hospitalization were collected up to June 2012.
Main Results:
- Of 840 patients, 14.4% (121) developed clinical MRSA infection, with a median time to infection of 22 days.
- 71.9% of infections occurred within 60 days of MRSA detection, but 14.0% occurred over six months later.
- Common infection sites included skin/soft tissue (40.5%), respiratory tract (30.6%), and bone/joint (11.6%). Crude mortality was higher in infected patients.
Conclusions:
- The risk of clinical MRSA infection is highest shortly after MRSA acquisition.
- Preventing MRSA acquisition in hospital settings is crucial for reducing patient morbidity and mortality.
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