Utility and Limitations of an Aggregate Community Antibiogram, Dallas County, Texas, 2009 – 2015

Background: Effective antimicrobial stewardship requires knowledge of local antibiotic resistance patterns, given geographic variations in antimicrobial susceptibility. Aggregating hospital antibiogram data has been recommended as an accurate method of monitoring community-specific antimicrobial resistance trends. We describe our experience with the practical utility and limitations of such community-level antibiograms over 6 years.

Methods: From 2009 to 2015, antimicrobial susceptibility data from 95% (18/19) of acute care hospitals in Dallas County with facility-specific antibiograms were analyzed according to Clinical and Laboratory Standard Institute guidelines, to generate an aggregate antibiogram disseminated annually. Trends in proportions of resistant isolates were analyzed using SAS 9.4. Participating hospitals were surveyed with standardized questionnaires regarding the perceived usefulness of this community antibiogram.

Results: Antibiotic susceptibility of the following 4 most frequently isolated organisms remained stable in 2014 compared to the prior 5 years: E. coli (n=21,183) to ceftriaxone (93%), meropenem (>99%), and ciprofloxacin (70%); K. pneumoniae (n=4,758) to ceftriaxone (92%) and meropenem (>99%); S. aureus (n=10,002) to methicillin (49%); S. pneumoniae (n=641) to penicillin (88%); E. faecium (n=955) to vancomycin (34%); and E. cloacae (n=1,237) to meropenem (98%). Susceptibility of P. aeruginosa(n=3,603) to piperacillin-tazobactam declined slightly in 2014 to 82% from the prior 3-year average of 86% (p<0.001). Survey respondents agreed that the county antibiogram was a valuable tool to monitor antimicrobial resistance trends on a community level, and to facilitate comparisons with hospital-specific antibiograms.

Conclusion: Our experience supports that an aggregate county antibiogram has been a sustainable and efficient tool for surveillance of local trends in antimicrobial resistance among bacteria of public health importance, and to provide awareness of baseline trends to area healthcare providers. Utilization of the community antibiogram to additionally serve as a resource to guide presumptive antimicrobial therapy in healthcare settings without facility-specific antibiograms, or to directly prompt changes in practice, however, is currently limited.