Changes in incidence and etiology of early-onset neonatal infections 1997-2017-a retrospective cohort study in western Sweden

Background The objective of the study was to evaluate data on early-onset neonatal invasive infections in western Sweden for the period 1997-2017. To identify changes in incidence, etiology and mortality and compare to previous studies from the same area starting from 1975. Methods Observational epidemiological, retrospective study on infants 0-6 days of age with a positive culture in blood and/or cerebrospinal fluid between 1997 and 2017. A comparison was made of the incidence between 2008 and 2017 compared to 1997-2007. Changes in the incidence of infections due to Group B streptococci, Staphylococcus aureus and aerobic Gram-negative rods were assessed from 1975. Results The total incidence, including both recognized pathogens and commensals as causative agents, was 1.1/1000 live births. The incidence declined from 1.4/1000 LB in 1997-2007 to 0.9/1000 LB in 2008-2017 but the case-fatality rate remained unchanged, (8/119 vs 7/90), at 7%. Among the 209 patients identified during 1997-2017 with sepsis or meningitis the most common organisms were Group B streptococci (40%, 84/209), S. aureus (16%, 33/209) and E. coli (9%, 18/209). The incidence of Group B streptococci infections went from 0.9/1000 live births 1987-1996 to 0.45/1000 live births 1997-2017 and all cases were within 72 h. The proportion of extremely preterm infants (< 28 weeks gestation) rose steadily during the study period but there was no rise in infections due to Gram-negative organisms. The spectrum of cultured organisms changed after 72 h as commensal organisms started to emerge. Conclusion There has been a decrease in the incidence of neonatal early-onset infections compared to previous studies in western Sweden. The incidence of GBS infections was not as low as in other reports. Further studies are needed to assess if screening-based intra partum antimicrobial prophylaxis instead of a risk factor-based approach for identifying candidates for intrapartum antimicrobial prophylaxis would be a better option for this study area. Key notes This study is one of the longest running follow-ups in the world, a follow-up of 43 years of early-onset neonatal infections. The incidence of early-onset GBS infections is higher in Western Sweden compared to other local reports. No difference in the incidence of early-onset GBS depending on the definition of early-onset being within 72 h or 7 days of life.