Factors associated with antimicrobial choice for surgical prophylaxis in Australia

Cefazolin is the most commonly recommended antimicrobial for surgical antimicrobial prophylaxis (SAP). However, the Australian Surgical National Antimicrobial Prescribing Survey revealed a wide range of antimicrobials prescribed for SAP. Inappropriate use of broad-spectrum antimicrobials is associated with increased patient harm and is a posited driver for antimicrobial resistance.

To describe patient, hospital and surgical factors that are associated with appropriateness of the top five prescribed antimicrobials/antimicrobial classes for procedural SAP.

All procedures audited from 18 April 2016 to 15 April 2019 in the Surgical National Antimicrobial Prescribing Survey were included in the analysis. Estimated marginal means analyses accounted for a range of variables and calculated a rate of adjusted appropriateness (AA). Subanalyses of the top five audited antimicrobials/antimicrobial classes identified associations between variables and appropriateness.

A total of 12 419 surgical episodes with 14 150 prescribed initial procedural doses were included for analysis. When procedural SAP was prescribed, appropriateness was low (57.7%). Allergy status, surgical procedure group and the presence of prosthetic material were positively associated with cefazolin and aminoglycoside appropriateness (P < 0.05). There were no significant positive associations with glycopeptides and third/fourth-generation cephalosporins. The use of broad-spectrum antimicrobials was the most common reason for inappropriate choice (67.9% of metronidazole to 83.3% of third/fourth-generation cephalosporin prescriptions).

Various factors influence appropriateness of procedural SAP choice. Identification of these factors provides targets for antimicrobial stewardship interventions, e.g. procedures where surgeons are regularly prescribing broad-spectrum SAP. These can be tailored to address local hospital prescribing practices.