Comparison of antibiograms developed for inpatients and primary care outpatients

To support antimicrobial stewardship, some healthcare systems have begun creating outpatient antibiograms. We developed inpatient and primary care outpatient antibiograms for a regional health maintenance organization (HMO) and academic healthcare system (AHS). Antimicrobial susceptibilities from 16,428 Enterococcus, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa cultures from 2010 were summarized and compared. Methicillin susceptibility among S. aureus was similar in inpatients and primary care outpatients (HMO: 61.2% versus 61.9%, P = 0.951; AHS: 62.9% versus 63.3%, P > 0.999). E. coli susceptibility to trimethoprim/sulfamethoxazole was also similar (HMO: 81.8% versus 83.6%, P = 0.328; AHS: 77.2% versus 80.9%, P = 0.192), but ciprofloxacin susceptibility differed (HMO: 88.9% versus 94.6%, P < 0.001; AHS: 81.2% versus 90.6%, P < 0.001). In the HMO, ciprofloxacin-susceptible P. aeruginosa were more frequent in primary care outpatients than in inpatients (91.4% versus 79.0%, P = 0.007). Comparison of cumulative susceptibilities across settings yielded no consistent patterns; therefore, outpatient primary care antibiograms may more accurately inform prudent empiric antibiotic prescribing.