Antibiotic spectrum index as an antimicrobial stewardship tool in paediatric intensive care settings

Antibiotic spectrum index (ASI) is a recently developed antimicrobial stewardship (AMS) tool that aims to classify antibiotics based on activity against clinically relevant bacterial pathogens.

We utilised ASI in a 2-year retrospective study between April 2019 and April 2021 in four paediatric intensive care units of a specialist UK children's hospital to quantify antibiotic use based on age, presence of immunosuppression and AMS input. We then compared ASI to days of therapy (DOT) to determine the utility of this AMS metric. We have made changes to Gerber's original ASI list and score of antibiotics to align with prescribing and resistance patterns in the UK.

Median ASI/antibiotic days increased with age: for infants under 1 year of age 4.1 (IQR 4.0-4.3), for children 1-5 years 4.4 (IQR 4.0-4.6) and for children over 5 years 4.5 (IQR 4.1-4.6). Immunocompromised patients received much broader-spectrum antibiotics than immunocompetent patients throughout the whole study period. Patients who had AMS input had a higher ASI compared with those who did not throughout the whole period, likely due to more complex patients being discussed on such rounds.

Our results show a complex picture of changing antibiotic consumption and prescribing in a large specialist paediatric hospital in the UK with a long-standing AMS programme before and throughout the COVID-19 pandemic. ASI shows less variability than DOT and can potentially be used to identify patient groups and time periods where broader-spectrum antibiotics are used to help guide further AMS efforts.