Temporal Trends of Escherichia coli Antimicrobial Resistance and Antibiotic Utilization in Australian Long-Term Care Facilities.

Background/Objectives: Antimicrobial resistance (AMR) is a global problem with antibiotic consumption considered a key modifiable factor for the development of AMR. Long-term care (LTC) facilities have been identified as potential reservoirs for Escherichia coli (E. coli) resistance due to high rates of urinary tract infection (UTI) and high levels of antibiotic consumption among residents. However, while the relationship between these two factors is well accepted, little is known about the possible temporal relationship between these. This study explores trends in E. coli resistance and antibiotic consumption in LTC focused on potential temporal relationships between antibiotic utilization and AMR.

Methods: A retrospective, longitudinal, and ecological analysis was conducted between 31 May 2016 and 31 December 2018. The primary outcomes were the monthly prevalence of E. coli AMR in urine isolates and the monthly percentage of residents using an antibiotic recommended for the management of UTI in national treatment guidelines (amoxicillin, amoxicillin with clavulanic acid, cefalexin, norfloxacin, and trimethoprim).

Results: During the study period, 10,835 urine E. coli isolates were tested, and 3219 residents received one or more medicines and were included in the medicines dataset. Over one-quarter were resistant to at least one of the target antibiotics (23.3%). For most antibiotics, the temporal relationship between AMR and antibiotic utilization was unclear; however, potential patterns were observed for both trimethoprim and amoxicillin with clavulanic acid. Trimethoprim showed a temporal decrease in both AMR and utilization, while amoxicillin with clavulanic acid showed a lag time of approximately four months between utilization and resistance.

Conclusions: The dynamic nature of AMR demonstrated in this study highlights the need for more up-to-date local surveillance to inform antibiotic choice in this setting.