PC1130: Patient Characteristics and Outcomes of Staphylococcus aureus bacteremia in a Quaternary NICU

Background: Despite progress in infection prevention, Staphylococcus aureus (SA) remains a leading cause of infections in NICUs. Invasive infections secondary to both methicillin sensitive (MSSA) and methicillin resistant SA (MRSA) contribute significantly to morbidity and mortality, especially among critically ill premature and low birth weight infants who require complex interventions for survival. Hence, the objective of this study is to identify risk factors for SA bacteremia in a level IV NICU and to compare outcomes between MSSA andMRSA infected infants.

Methods: We reviewed medical records of patients in the Children’s Hospital of Philadelphia NICU who underwent sepsis evaluations from January 2017 – November 2021. Statistical analysis included summary statistics, Chi-square tests, Fisher’s exact tests, Wilcoxon rank-sum, Kruskal Wallis tests, and a statistical process control P chart to measure variation in SA infection over time.

Results: Among 3297 sepsis evaluations from 2017-2021, 177 (4%) had bacteremia. SA accounted for 33% (n=59) of all bacteremia cases, the majority caused by MSSA (n=49, 83%). There was no statistically significant change in the percent of SA isolates over time (Image 1). Patients with SA bacteremia were more likely to be preterm (p 0.001) and have lower birth weight (p 0.006) compared to patients without bacteremia (Table 1). Compared to infants with non-SA infections, SA bacteremia patients were more likely to require oscillator support (36% vs. 19%, p< 0.001), steroids (32% vs. 20%, p 0.02), and central lines (73% vs. 59%, p 0.02) (Table 1). SA bacteremia was also associated with longer length of stay among survivors compared to non-SA infections (median 142 days vs. 125 days, p 0.02). All-cause mortality was similar in patients with MRSA bacteremia (30%) compared to MSSA (29%). Non-survivors with SA infections were more likely than survivors to require ventilatory support (100% vs. 58%, p 0.001), vasoactive medications (53% vs. 16%, p 0.004), and steroids (59% vs. 18%, p 0.003).

Conclusion: In our level 4 NICU, SA bacteremia is associated with prematurity, low birthweight, and frequent use of complex medical interventions, devices, and cardiorespiratory support. While MSSA infections are more common, both MSSA and MRSA bacteremia are associated with considerable mortality. There is urgent need for efforts targeted towards prevention of SA in critically ill infants. Next steps include investigating and mitigating SA colonization in our NICU and monitoring the impact of interventions on rates of invasive infection.