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Association between respiratory tract methicillin-resistant Staphylococcus aureus and survival in cystic fibrosis

Elliott C Dasenbrook¹, William Checkley, Christian A Merlo

¹Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, Case Western Reserve University School of Medicine and University Hospitals Case Medical Center, Cleveland, Ohio 44106-5067, USA. ecd28@case.edu

|June 17, 2010

Abstract

Context:

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in the respiratory tract of individuals with cystic fibrosis (CF) has increased dramatically; however, its impact on outcomes in CF is unclear. Because the time between infection with bacteria in CF and death can be decades, observational studies with long periods of follow-up are well suited to address the current gap in knowledge.

Objective:

To determine whether isolation of MRSA from the respiratory tract of CF patients is associated with worse survival compared with patients who never have a culture positive for MRSA.

Design, Setting, And Participants:

Cohort study of 19,833 CF patients aged 6 to 45 years seen at centers accredited by the Cystic Fibrosis Foundation in the United States. Patients entered between January 1996 and December 2006 and were followed up through December 2008. Cox regression models with time-varying covariates were used to compare survival between CF patients with and without respiratory tract MRSA.

Main Outcome Measure:

Time from age at entry until age at death from any cause.

Results:

In 137,819 patient-years of observation (median, 7.3 years/patient), 2537 CF patients died and 5759 patients had MRSA detected. The mortality rate was 18.3 deaths (95% confidence interval [CI], 17.5-19.1) per 1000 patient-years in patients without MRSA and 27.7 deaths (95% CI, 25.3-30.4) per 1000 patient-years in those with MRSA. Among those with MRSA, the attributable risk percentage of death associated with MRSA was 34.0% (95% CI, 26.7%-40.4%). The unadjusted hazard ratio associated with MRSA was 1.47 (95% CI, 1.32-1.62). After adjustment for time-varying covariates associated with severity of illness, MRSA remained associated with a higher risk of death (1.27; 95% CI, 1.11-1.45).

Conclusion:

Detection of MRSA in the respiratory tract of CF patients was associated with worse survival.

Insights

Methicillin-resistant Staphylococcus aureus (MRSA) detection in cystic fibrosis (CF) patients is linked to increased mortality. This study highlights the significant impact of MRSA on survival rates in individuals with CF.

Area of Science:

Pulmonary Medicine
Infectious Diseases
Clinical Epidemiology

Background:

Increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in the respiratory tracts of cystic fibrosis (CF) patients.
Uncertainty regarding the impact of MRSA on CF patient outcomes.
Need for long-term observational studies due to the decades-long timeline between infection and mortality in CF.

Purpose of the Study:

To investigate the association between respiratory tract MRSA isolation and survival in CF patients.
To compare survival rates of CF patients with and without MRSA detection.
To quantify the impact of MRSA on mortality risk in the CF population.

Main Methods:

A cohort study involving 19,833 CF patients aged 6-45 years in US-accredited centers.
Patient data collected between January 1996 and December 2006, with follow-up through December 2008.
Cox regression models with time-varying covariates were employed to analyze survival data.

Main Results:

Over 137,819 patient-years, MRSA was detected in 5,759 patients, and 2,537 CF patients died.
Mortality rates were higher in patients with MRSA (27.7/1000 patient-years) compared to those without (18.3/1000 patient-years).
MRSA was independently associated with a 27% increased risk of death (adjusted hazard ratio, 1.27; 95% CI, 1.11-1.45).

Conclusions:

Detection of MRSA in the respiratory tract of CF patients is significantly associated with poorer survival.
MRSA contributes to an increased mortality risk in individuals with cystic fibrosis.
These findings underscore the importance of monitoring and managing MRSA in CF care.

Read full analysis

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