Comparison of hospital-wide and age and location - stratified antibiograms of S. aureus, E. coli, and S. pneumoniae: Age- and location-stratified antibiograms

Abstract

Background: Antibiograms created by aggregating hospital-wide susceptibility data from diverse patients can be misleading. To demonstrate the utility of age- and location-stratified antibiograms, we compared stratified antibiograms for three common bacterial pathogens, E. coli, S. aureus, and S. pneumoniae. We created stratified antibiograms based on patient age (<18 years, 18-64 years, >/=65 years), and inpatient or outpatient location using all 2009 E. coli and S. aureus, and all 2008-2009 S. pneumoniae isolates submitted to our clinical microbiology laboratory. We compared susceptibility rates among cumulative and stratified antibiograms using descriptive statistics. Findings: For E. coli and S. aureus, the institution-wide antibiogram overestimated resistance in pediatic isolates and underestimated resistance in isolates from the elderly. For E. coli, pediatric isolates were less susceptible to ampicillin and ampicillin-sulbactam and more susceptible to gentamicin and ciprofloxacin compared to adult isolates (p < 0.05 for all), and isolates from patients >65 years were least susceptible to ciprofloxacin (71%). For S. aureus, susceptibility to oxacillin, clindamycin, and levofloxacin was highest among children and decreased with increasing age (p