Difference in the impact of coinfections and secondary infections on antibiotic use in patients hospitalized with COVID-19 between the Omicron-dominant period and the pre-Omicron period.

Introduction: This study evaluated the effect of coinfections and/or secondary infections on antibiotic use in patients hospitalized with coronavirus disease 2019 (COVID-19).

Method: Days of therapy per 100 bed days (DOT) in a COVID-19 ward were compared between 2022 (Omicron period) and 2021 (pre-Omicron period). Antibiotics were categorized as antibiotics predominantly used for community-acquired infections (CAIs) and antibiotics predominantly used for health care-associated infections (HAIs). Bacterial and/or fungal infections which were proved or assumed on admission were defined as coinfections. Secondary infections were defined as infections that occurred following COVID-19.

Results: Patients with COVID-19 during the Omicron period were older and had more comorbidities. Coinfections were more common in the Omicron period than in the pre-Omicron period (44.4% [100/225] versus 0.8% [2/257], respectively, p < 0.001), and the mean DOT of antibiotics for CAIs was significantly increased in the Omicron period (from 3.60 to 17.84, p < 0.001). Secondary infection rate tended to be higher in the Omicron period (p = 0.097). Mean DOT of antibiotics for HAIs were appeared to be lower in the COVID-19 ward than in the general ward (pre-Omicron, 3.33 versus 6.37, respectively; Omicron, 3.84 versus 5.22, respectively). No multidrug-resistant gram-negative organisms were isolated in the COVID-19 ward.

Conclusion: Antibiotic use for CAIs was limited in the pre-Omicron period but increased in the Omicron period because of a high coinfection rate on admission. With the antimicrobial stewardship, excessive use of antibiotics for HAIs was avoided in the COVID-19 ward during both periods.