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.