Seasonal variation in intravenous broad-spectrum antimicrobial use in Japan from 2018 to 2023.

Background: To date, no studies have specifically addressed seasonal variation in the use of intravenous broad-spectrum antimicrobials. This study aimed to examine the seasonal patterns of the use of intravenous broad-spectrum antimicrobials by utilizing a nationwide Japanese infection control surveillance database.

Methods: This retrospective cohort study extracted the days of therapy (DOT) for intravenous broad-spectrum antimicrobials and the detection rates of drug-resistant bacteria from the database between 2018 and 2023. Seasonal variation was analyzed using these values through seasonal and trend decomposition using loess.

Results: The DOT for carbapenems, tazobactam/piperacillin, fourth-generation cephalosporins, and fluoroquinolones showed seasonal variation, peaking in fall. Conversely, no significant seasonal variation was observed in the DOT for anti-methicillin-resistant Staphylococcus aureus (MRSA) agents. The detection rates of Pseudomonas aeruginosa, Klebsiella aerogenes, and Enterobacter cloacae exhibited seasonal variation and peaked in fall. The detection rates of Enterococcus faecium exhibited seasonal variation as well, though no distinct peaks were observed. There was no significant seasonal variation in the detection rates of third-generation cephalosporin-resistant Escherichia coli or MRSA.

Conclusion: The findings of this study indicate seasonal variation in the use of intravenous broad-spectrum antimicrobials. This seasonality was likely influenced by various factors, including the detection rates of drug-resistant bacteria. The study underscores the importance of appropriate antimicrobial stewardship and interventions against drug-resistant organisms, particularly during fall.