s.aureus surveillance and decolonization in the nicu 883
admission. A neonate was considered to have a bloodstream infection (BSI) if a blood culture grew S. aureus. Incidence rates for NICU-attributable S. aureus clinical cultures and BSIs and 95% confidence intervals (CI) were calculated for the pre- and post-intervention periods and were compared using 2-sample Poisson tests. Interrupted time series models were fit to the log-transformed quarterly incidence rates to quantify the immediate impact of the program, and the relative change in incidence rates per quarter during the pre- and postintervention period.4 Our institutional review board approved this study.
results
During the 24months before implementation of the intervention (29,200 patient days) and 39months post-implementation (47,135 patient days), 74 and 68 NICU-attributable S. aureus clinical cultures occurred, respectively. There were 116 unique patients with 142 S. aureus cultures, of which 131 (92%) were MSSA and 11 (8%) were MRSA. Sources for the 142 isolates included 84 (59.2 %) respiratory, 20 (14%) blood, 10 (7.0%) conjunctiva, 11 (7.7%) wound, 7 (4.9%) other, 5 urine (3.5%), 3 abscess (2.1%), and 2 cerebral spinal fluid (1.4%). In the post-intervention period, 1,847 neonates were screened for S. aureus colonization as part of the ASC and decolonization program. Of the 333 colonized patients, 243 were treated with mupirocin. Overall, a 43% reduction in the incidence rate of S. aureus
clinical isolates occurred when comparing the post- to the pre-intervention period (IRR, 0.57; 95% CI, 0.40–0.80) (Figure 1a). Prior to the intervention, the incidence rate of S. aureus clinical cultures was estimated to increase at a nonsignificant rate of 14% per quarter (IRR, 1.14; 95% CI, 0.95–1.38). In the quarter following introduction of MSSA to the ASC program, we observed an immediate 65% decrease (IRR, 0.35; 95% CI, 0.15–0.82); thereafter, we observed an estimated 2.0% quarterly decrease in the incidence of NICU- attributable S. aureus clinical cultures (IRR, 0.98; 95% CI, 0.92–1.05). The rate at which the incidence rates changed over time during the pre- and post-intervention periods did not differ statistically (estimated relative quarterly rate of change, 0.86; P = .12). Prior to the intervention, there was no change in the
incidence rate of BSIs (IRR, 1.00; 95% CI, 0.78–1.29). After implementation, there were statistically nonsignificant reductions (1) in the overall incidence rate of S. aureus BSIs (IRR, 0.50; 95% CI, 0.18–1.34) (Figure 1b), (2) in the immediate change in rate of S. aureus BSIs (IRR, 0.73; 95% CI, 0.20–2.58), and (3) in the quarterly incidence rate of S. aureus BSIs (IRR, 0.97; 95% CI, 0.92–1.03). With an average of 5.5 BSIs per year in the pre-intervention
period, 18 BSIs were expected to occur in the post-intervention period, yet we observed 9. In the setting of ≥70% compliance with the decolonization protocol, 50% fewer infections occurred than expected, suggesting that 27 neonates were treated to prevent 1 BSI.
discussion
Our data suggest that an active MSSA screening and decoloni- zation program in the NICU can lead to a sustained reduction (43% overall) in the incidence of clinical S. aureus isolates. Prior studies have found that ASC and decolonization, in
conjunction with other infection control measures, can reduce MRSA colonization and infection.2,5 The burden of MSSA infections exceeds that of MRSA infections in theNICU,3 yet few studies have examined the impact of MSSA ASC and decoloni- zation. Recently, Wisgrill et al6 reported promising results of an MSSA surveillance and decolonization program that led to a 50% reduction of MSSA-attributable infections in very low-birth- weight infants. Our study reports similar findings, and we included all neonates admitted to the NICU to reflect the impact on overall burden of S. aureus HAIs. Efficacy, cost-effectiveness, and safety influence the decision
to perform ASCs and decolonization. While neonatal data are limited, reports from adult populations suggest that active surveillance, targeted decolonization, and at times, universal decolonization are cost-effective compared to other preven- tion methods.7 Possible unintended consequences of decolo- nization include replacing S. aureus with more virulent pathogens. However, in a multicenter NICU study examining MRSA decolonization, patients treated with mupirocin did not show increased risk of novel gram-negative and fungal infections.8 Emerging resistance to mupirocin must also be considered with widespread use, but recent S. aureus ASC and decolonization programs have not found an increase in resistance to mupirocin.4–6,9 Incorporating MSSA screening into a NICU’s infection
control protocolmay be an important step to reduce S. aureus infections in this vulnerable neonatal population.
acknowledgments
The authors would like to thank Qumars Roshanian of The Johns Hopkins Pathology Data Services for his assistance in extracting microbiology culture data aswell as AvinashGadala of The JohnsHopkins Hospital Department of Hospital Epidemiology and Infection Control for his assistance with data management. Financial support: This study was partially funded by the Agency for Healthcare Research and Quality (AHRQ grant no. 1R01HS022872). Potential conflicts of interest: A.M. and J.J. report grant support from Sage
Products (Cary, IL). All other authors report no conflicts of interest. Annie Voskertchian, MPH;1
Ibukunoluwa C. Akinboyo, MD;1 Elizabeth Colantuoni, PhD;3 Julia Johnson, MD;2
Aaron M. Milstone, MD, MHS1 Affiliations: 1. Division of Infectious Disease, Department of Pediatrics,
Johns Hopkins University, Baltimore, Maryland; 2. Division of Neonatology, Department of Pediatrics, Johns Hopkins University, Baltimore, Maryland; 3. Department of Biostatistics, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland. Address correspondence to Aaron M. Milstone, MD, MHS, 200N Wolfe St, Baltimore MD 21287 (
amilsto1@jhmi.edu).
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