MRSA Nasal Carriage Patterns and the Subsequent Risk of Conversion between Patterns, Infection, and Death

Abstract

BackgroundPatterns of methicillin-resistant S. aureus (MRSA) nasal carriage over time and across the continuum of care settings are poorly characterized. Knowledge of prevalence rates and outcomes associated with MRSA nasal carriage patterns could help direct infection prevention strategies. The VA integrated health-care system and active surveillance program provides an opportunity to delineate nasal carriage patterns and associated outcomes of death, infection, and conversion in carriage.Methods/FindingsWe conducted a retrospective cohort study including all patients admitted to 5 acute care VA hospitals between 2008–2010 who had nasal MRSA PCR testing within 48 hours of admission and repeat testing within 30 days. The PCR results were used to define a baseline nasal carriage pattern of never, intermittently, or always colonized at 30 days from admission. Follow-up was up to two years and included acute, long-term, and outpatient care visits. Among 18,038 patients, 91.1%, 4.4%, and 4.6% were never, intermittently, or always colonized at the 30-day baseline. Compared to non-colonized patients, those who were persistently colonized had an increased risk of death (HR 2.58; 95% CI 2.18;3.05) and MRSA infection (HR 10.89; 95% CI 8.6;13.7). Being in the non-colonized group at 30 days had a predictive value of 87% for being non-colonized at 1 year. Conversion to MRSA colonized at 6 months occurred in 11.8% of initially non-colonized patients. Age >70 years, long-term care, antibiotic exposure, and diabetes identified >95% of converters.ConclusionsThe vast majority of patients are not nasally colonized with MRSA at 30 days from acute hospital admission. Conversion from non-carriage is infrequent and can be risk-stratified. A positive carriage pattern is strongly associated with infection and death. Active surveillance programs in the year following carriage pattern designation could be tailored to focus on non-colonized patients who are at high risk for conversion, reducing universal screening burden.

Methicillin-resistant Staphylococcus aureus carriage screening in intensive care

“…MRSA screening is routinely employed in many countries world-wide and is thought to be helpful in limiting MRSA spread. [156] However, in developing nations including India, universal active surveillance is expected to be resource and labor intensive and its benefits need to be appropriately weighed with respect to the outcomes obtained and its cost-effectiveness. Targeted surveillance may also be tested as a viable alternative in our settings, wherein the screening can be focused on patients who are more likely to convert to an MRSA colonized pattern, such as those in long-term care, greater than 70 years of age, having diabetes or antibiotic exposure.…”

“…Targeted surveillance may also be tested as a viable alternative in our settings, wherein the screening can be focused on patients who are more likely to convert to an MRSA colonized pattern, such as those in long-term care, greater than 70 years of age, having diabetes or antibiotic exposure. [6]…”

Active Surveillance of Methicillin-Resistant <i>Staphylococcus aureus</i> Using a Fully Automated Molecular Test in an Emergency Medical Center

“…A retrospective cohort study reported that the MRSA infection rate was 14.4z in newly colonized patients in an intensive care unit (7). Another study utilizing a nasal PCR screening test for MRSA demonstrated that patients colonized with MRSA had an increased risk of infection and death, compared to non-colonized patients (8). Therefore, the prevention of MRSA colonization is important for preventing subsequent MRSA infections, and preventing this colonization can lead to decreased morbidity and mortality.…”

The Microbiome at Other Mucosal Sites

“…Different species of staphylococci are present in the nasal microbiome, principally Staphylococcus aureus and S. epidermidis (Frank et al, 2010). The nasal mucosa is known for its carriage of the methicillin-resistant S. aureus (Gupta et al, 2013). Although S. aureus can act as commensal in the healthy nasal microbiome, some virulent strains can grow at higher rates and affect the community structure, diminishing the abundance of the commensals Propionibacterium acnes and S. epidermidis (Frank et al, 2010).…”