By Stan Deresinski, MD, FACP, FIDSA

Clinical Professor of Medicine, Stanford University

Dr. Deresinski reports no financial relationships relevant to this field of study.

SYNOPSIS: Although the rate of hospital-onset MRSA bacteremia has decreased since 2012, the rate of decrease has slowed. The National Action Plan goal of a 50% reduction by 2012 compared to 2015 seems out of reach.

SOURCE: Kourtis AP, Hatfield K, Baggs J, et al; Emerging Infections Program MRSA author group. Vital Signs: Epidemiology and recent trends in methicillin-resistant and in methicillin-susceptible Staphylococcus aureus bloodstream infections — United States. MMWR Morb Mortal Wkly Rep 2019;68:214-219.

Staphylococcus aureus, both methicillin-susceptible (MSSA) and resistant (MRSA), are among the most important bacterial pathogens in the community and in healthcare facilities. The Centers for Disease Control and Prevention (CDC) has evaluated the epidemiological trends in bloodstream infections (BSI) caused by each of these pathogens from 2012 to 2017 in the United States. To accomplish this, they examined both the Emerging Infections Program (EIP) MRSA and the Premier and Cerner Electronic Health Record (EHR) databases. (See Figures.)

Figure 1: Adjusted Methicillin-Resistant Staphylococcus aureus Bloodstream Infection Rates 2005-2016

Figure 1

Source: Centers for Disease Control and Prevention

Figure 2: Adjusted Hospital-Onset and Community-Onset Rates of Staphylococcus aureus Bloodstream Infection — Premier and Cerner Hospitals, United States, 2012-2017

Figure 2

 

Source: Centers for Disease Control and Prevention

Based on EIP surveillance data, the incidence of hospital-onset MRSA BSI decreased by 74% from 2005 to 2016, while that of community-onset cases decreased by 40%. Although the rates of hospital-onset bacteremia decreased by 17.1% annually during that time, the rate of decline diminished beginning in 2013 such that the reduction was not statistically significant (P = 0.25). The annual rate of decline for community-onset MRSA bacteremia was 6.9%, with much of this decrease due to a reduced occurrence of healthcare-associated infections, which decreased by 7.8% annually.

Based on EHR data from 447 hospitals, adjusted hospital-onset MRSA BSI decreased at a rate of 7.3% per year (P < 0.0001) with no significant change in community-onset MRSA BSI. At the same time, there was no significant change in hospital-onset MSSA rates, while community-onset MSSA BSI rates increased 3.9% annually (P < 0.001). The unadjusted overall in-hospital mortality rates for all S. aureus BSI was 18% and was higher for hospital-onset than community-onset cases.

The CDC estimated that 119,247 cases of S. aureus BSI occurred in the United States in 2017 and that there were 19,832 associated deaths.

COMMENTARY

One contribution of this analysis is that related to MSSA BSI — something for which national data largely has been missing. This report indicates that the rates of hospital-onset MSSA BSI have not changed significantly since 2012, while there may have been a slight increase in that of community-onset MSSA BSI — findings that contrast to those regarding MRSA BSI.

The U.S. National Action Plan to Prevent Health Care-Associated Infections calls for a 50% reduction in hospital-onset MRSA BSI in 2020 compared to the rate in 2015.1 Despite the observed (albeit recently slowed) progress, this goal is unlikely to be achieved. The CDC stresses the need to continue effective infection control practices that have been implemented contemporaneously with the observed decrease in hospital-onset BSI infections — the chief of which, in my opinion, was the introduction of alcohol gels making handwashing more convenient.

One question that can be raised is that since many infection control practices, such as handwashing, central line bundles, and the like, are not organism-specific, why was there not a decrease in MSSA BSI? The CDC also suggests greater implementation of decolonizing activities, which are MRSA-specific, but which remain somewhat controversial. 

REFERENCE

  1. Office of Disease Prevention and Health Promotion, Department of Health and Human Services. National Action Plan to Prevent Health Care-Associated Infections: Road Map to Elimination. Available at: https://health.gov/hcq/prevent-hai-action-plan.asp#phase4. Accessed April 11, 2019.