Trends in Incidence of Methicillin-Resistance Staphylococcus aureus Central Line- Associated Bloodstream Infections in U.S. Neonatal Intensive Care Units, 1998–2008

Background:

Methicillin-resistant Staphylococcus aureus (MRSA) is challenging to treat in neonates and is associated with significant morbidity and mortality. Although decreases in MRSA central line-associated bloodstream infections (CLABSIs) in adult and pediatric ICUs in the United States have been recently documented, it is unclear if this same trend has occurred in NICUs.  

Objective:

Assess trends in incidence of MRSA and methicillin susceptible S.aureus (MSSA) CLABSIs in U.S. NICUs using the most recent 10 years of surveillance data from CDC's National Nosocomial Infections Surveillance System (NNIS) and National Healthcare Safety Network (NHSN)

Methods:

We analyzed CLABSI surveillance data reported to NNIS from 1998-2004 and to NHSN 2006-2008. Surveillance data were not available for 2005. MRSA CLABSI pooled mean annual incidence rates (CLABSI/10,000 central-line days) were calculated by pooling data across all NICUs by each birthweight category and calendar year. Percent of MRSA was defined as the proportion of S. aureus CLABSIs tested for methicillin or oxacillin that were reported resistant.   We used Poisson regression to estimate changes in incidence over the analysis period. We performed a sensitivity analysis to confirm findings by limiting Poisson regression to NICUs reporting at least 1 month of data and 50 central-line days in each year of the analysis period.

Results:

From 1998 through 2008, 332 NICUs reported 1,371 S.aureus CLABSIs among 2,461,738 central-line days. Of the 1,270 S.aureus with susceptibility results to methicillin or oxacillin, 371 (29%) were MRSA. Sixty percent of MRSA CLABSIs occurred among neonates weighing ≤ 1000g at birth. Despite year to year fluctuations, combining all birthweight categories, MRSA CLABSI incidence increased by 49.6% (95% CI, +11.6% to +101.2%; P=0.007) from 1998 to 2008 (1.1 to 1.6 per 10,000 central- line days). When stratified by birthweight categories, increases were statistically significant only among babies between 1001g-1500g (P=0.008) (Table). When limited to 46 NICUs reporting continuously throughout the analysis period, the increase remained significant; starting at 0.9 in 1998 to 1.3 per 10,000 central-line days in 2008 (+ 82.2%, 95% CI, + 14.7% to + 200.4%; P=0.01). During this time, MSSA CLABSI incidence fluctuated, but overall remained stable around 3.1 to 3.2 per 10,000 central-line days

(P=0.5).

Conclusions:

We observed a significant increase in incidence of MRSA CLABSI among NICU patients during a period where MSSA CLABSI did not change significantly. Understanding the reasons of this increase (e.g. differences in adherence to central line insertion practices, barriers for best practices, or need for NICU-specific interventions) may help develop effective targeted prevention strategies.