Use of Antibiotics and Severe Bacterial Infections Within the First 6 Months of Life-A Population-Based Cohort Study From East Denmark.

Aim: To investigate antibiotic exposure and the incidence of severe bacterial infections during the first 6 months of life in preterm infants born between 28 and 37 weeks of gestation.

Methods: Retrospective population-based study of preterm infants in East Denmark, 2019-2021. Participants were identified based on dispensed antibiotics through the joint electronic health system. Infectious episodes were defined as suspected (≤ 4 days of treatment), probable (≥ 5 days of treatment) or proven if blood culture positive.

Results: During the first 6 months of life, 557 of 5128 (11%) preterm infants received 635 courses. Two-thirds of all antibiotic courses were administered within the first 72 h of life, with 12 proven infections, that is, 2.3 per 1000 live births. Beyond 72 h of age, nearly all bacterial infection episodes were hospital acquired, with 24 proven infections, that is, 4.7 per 1000 live births. Three infants had sepsis-related mortality, that is, 0.58 per 1000 live births.

Conclusion: In preterm Danish infants aged 28-37 weeks of gestation, antibiotic treatment for suspected or probable infections was 15 times higher than for confirmed infections. Antibiotic exposure was high in this group of preterm infants, while confirmed infections were low.