Peri-Covid-19 Antibiotic Use and Antimicrobial Resistance in Older Adults

Antibiotic use during the coronavirus disease 2019 (Covid-19) pandemic was common in the outpatient setting, but was not supported by guidelines. We sought to evaluate the role of this antibiotic use on downstream antibiotic resistance.

We performed a population-wide cohort study of all nonhospitalized adults 66 years of age or older in Ontario, Canada, from January 1, 2020, to June 30, 2021, with a first identification of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We evaluated the relationship between outpatient peri-Covid-19 antibiotic exposure (within a period of 7 days before or after index SARS-CoV-2 reporting) and downstream isolation of an antibiotic-resistant organism from clinical culture within 6 months. We calculated adjusted odds ratios of the association between peri-Covid-19 prescribing and antibiotic-resistant organism detection, as well as the adjusted attributable fractions of downstream antibiotic-resistant organisms.

Of the 53,533 eligible individuals included, 8228 (15%) were prescribed a peri-Covid-19 antibiotic, and 1477 (3%) had a downstream antibiotic-resistant organism identified. The adjusted odds ratio for the presence of any antibiotic-resistant organism with peri-Covid-19 antibiotic use was 1.24 (95% confidence interval [CI], 1.09 to 1.41), while the adjusted odds ratio for the presence of gram-negative antibiotic-resistant organisms was 1.27 (95% CI, 1.11 to 1.46) and for gram-positive antibiotic-resistant organisms it was 1.02 (95% CI, 0.70 to 1.48). Among all individuals who received an antibiotic within 7 days of SARS-CoV-2 diagnosis, the attributable fraction of downstream antimicrobial resistance related to peri-Covid-19 antibiotic use was 17% (95% CI, 7 to 26%). Among all individuals with a SARS-CoV-2 diagnosis, the population-attributable fraction of downstream antimicrobial resistance related to peri-Covid-19 antibiotic use was 4% (95% CI, 2 to 7%).

Peri-Covid-19 antibiotic use was associated with downstream antimicrobial resistance, and particularly the presence of gram-negative antibiotic-resistant organisms. (Funded by the Canadian Institutes of Health Research Operating Grant [grant number 179461] and others).