Bloodstream infections in young infants: a cohort study.

OBJECTIVE: The burden of bloodstream infection (BSI) is highest among infants. We aim to describe temporal trends in the incidence and characteristics of BSI in young infants. DESIGN: Birth cohort study. SETTING: Queensland, Australia. PATIENTS: All <90-day-old infants with culture-confirmed BSI detected by Pathology Queensland from 2000 to 2019. MAIN OUTCOME MEASURES: The annual incidence of BSI was calculated using live births in public hospitals. Infections were categorised as early onset (0≤3 days) or late onset (4<90 days). Comorbidities were defined using a paediatric complex chronic conditions classification system. Temporal trends were examined using time series models. RESULTS: In total, 2327 incident BSIs occurred in 2173 infants. Late-onset BSI comprised 67% (n=1568). Comorbidities were present in 25% (n=188) of early-onset and 48% (n=716) of late-onset BSI. Common pathogens were Escherichia coli (21%, n=501), Group B Streptococcus (GBS) (21%, n=493) and Staphylococcus aureus (14%, n=338). Overall incidence was 2.98 per 1000 live births (early-onset 1.01, late-onset 1.96), which increased over time (incidence rate ratio 1.01 (95% CI 1.00 to 1.01)). The incidence of Enterobacterales BSI increased by 1.96% each year (1.02 (1.01 to 1.03)) and GBS by 1.91% (1.02 (1.01, 1.04)). Early-onset GBS increased by 11% per year from 2014 to 2019 (1.11 (1.04 to 1.19)). The overall case fatality rate was 8.8% (early onset 6.4%, late onset 10%). CONCLUSIONS: The incidence of GBS and Enterobacterales BSI has risen in young infants in Queensland, especially for early-onset GBS since 2014. These findings highlight the increasing importance of Enterobacterales infections in young infants and the need to reconsider prevention strategies for early-onset GBS.