Regional-local urinary antibiograms for long-term care homes: a population-wide cross-sectional study

Antibiograms are challenging to construct in long-term care (LTC) homes in part due to low isolate counts and limited precision. Regional-local antibiograms offer a potential solution by using partial pooling, combining data from both the home and the broader LTC population. We developed regional-local urinary antibiograms and compared this approach to standard antibiograms. This cross-sectional study included urine cultures from LTC residents across Ontario. (i) Standard syndromic combined antibiograms were created for each LTC home with ≥30 total isolates. Homes with <30 isolates used the mean of susceptibility for each drug for the entire province. (ii) Partially pooled regional-local antibiograms were constructed using logistic mixed models with a random intercept for each home to ensure each LTC home could be provided a facility-specific antibiogram. We compared susceptibility and rank order of recommended antibiotics using each method. Among 627 LTC homes, 340 (54.2%) met the ≥30 isolate threshold. Regional-local methods allowed for the development of 627 LTC home-specific antibiograms. These methods narrowed susceptibility estimate ranges compared to standard methods (e.g., trimethoprim-sulfamethoxazole [TMP-SMX]: 57%–77% vs 37%–90%, respectively). A total of 119 (19.0%) homes had at least one antibiotic with over 80% susceptibility using the standard approach; only 11 (1.8%) homes met this threshold with the regional-local antibiogram. The antibiotic with the highest susceptibility varied based on methodology (amoxicillin-clavulanate for standard vs TMP-SMX for regional-local antibiogram). Regional-local antibiograms allow for the creation of facility-specific antibiograms, even among facilities with small isolate counts. This approach may provide more precise antibiotic susceptibility estimates by reducing misleading inter-facility variation.