Late-onset Neonatal Infections 1997 to 2017 Within a Cohort in Western Sweden-The Last 21 Years of a 43-Year Surveillance.

BACKGROUND The objective of the study was to assess the epidemiology of late-onset (LO) neonatal invasive infections with surveillance covering 43 years, starting from 1975. METHODS Observational epidemiologic, retrospective study including a cohort of infants born in western Sweden in 1997-2017, who had a positive blood and cerebral spinal fluid culture between 3 and 120 days of age. A comparison was made of the incidence between 1997-2007 and 2008-2017. Data on LO infections during 3-27 days of life were assessed from 1975. RESULTS A total of 473 cases of LO infections were registered in 437 patients. The incidence increased from 2.0 to 3.1/1000 live births (LB) between 1997-2007 and 2008-2017 (P < 0.001). The increase in incidence was most pronounced among infants born <28 weeks gestation (from 255 to 398/1000 LB, P < 0.001). The most frequent pathogens were Staphylococcus aureus (25%), coagulase-negative staphylococci (17%), and Escherichia coli (13%). Infections due to group B Streptococci rose from 0.16/1000 LB to 0.33 (P = 0.03). During the whole surveillance period from 1975 to 2017, there were 579 cases between 3 and 27 days of life. Although the incidence increased in 2008-2017 to 1.9/1000 LB after first declining in 1997-2007, the case-fatality rate continued to decline from 27/284 (9.5%) between 1975 and 1996 to 6/182 (3.3%) in 2008 and 2017 (P = 0.01). CONCLUSIONS The incidence of LO neonatal invasive infections increased during the study period (1997-2017), but the case-fatality rate remained lower than in the previous surveillance period (1975-1996). Further surveillance and interventions with focus on prevention is critical to counteract the increasing incidence among high-risk infants.