Methods: To achieve our objectives we designed a case control retrospective review of the electronic health records of all blood cultures collected on full term, previously healthy children age 3 months–3 years at KPNC from September 1st 1998 to August 31st 2014 in outpatient clinics, emergency departments and first 24 hours of hospitalization.
Results: During the study period, 54,260 blood cultures were collected in a population of 545,833 full term children 3 months – 3 years. By 2014, the incidence rate of bacteremia had decreased from 2.87 to 0.61 / 1000 full term births. Implementation of routine vaccination with the conjugated pneumococcal vaccine resulted in an 87.5% reduction of Streptococcus pneumoniae bacteremia (1.2% pre-Prevnar7® to 0.25% post-Prevnar7® / pre-Prevnar13® to 0.15% post-Prevnar13®) and a 40% reduction in overall bacteremia (1.5% pre-Prevnar7® to 0.73% post-Prevnar7® / pre-Prevnar13® to 0.9% post-Prevnar13®) in the study population. As pneumococcal rates decreased, Escherichia coli, Salmonella spp. and Staphylococcus aureus have surpassed S. pneumoniae as leading causes of bacteremia in this age.
The rate of blood culture isolation of contaminating organisms remained between 1.9 – 2.2%; therefore, by the end of the study, 71% of organisms identified in blood cultures were contaminants. During the 15 study years, total blood cultures drawn decreased by 78% and 49% in outpatient pediatric clinics and emergency departments, respectively.
Conclusion: In the United States, routine vaccinations have made bacteremia in the previously healthy toddler a rare event. As the incidence of pneumococcal bacteremia has decreased, E. coli, Salmonella spp. and S. aureus have increased in relative importance. New guidelines are needed to approach the previously healthy febrile toddler in the outpatient setting.