Antibiograms in resource limited settings: Are stratified antibiograms better?

Background Antibiograms often act as a reference guide for empirical selection of antibiotics. Hospital-wide antibiograms constructed on the basis of cumulative antimicrobial susceptibility data from diverse patient groups can often be misleading. In order to show the significance of age- and location-stratified antibiograms, this study compared hospital-wide antibiograms with stratified antibiograms for the clinical isolates of Pseudomonas aeruginosa. Methods Stratified antibiograms were created on the basis of patient age (<18 years, 18-50 years, >50 years) and location (inpatient or outpatient) using all 2011, 2012 and 2013 clinical isolates of P. aeruginosa isolates. Susceptibility rates were compared among cumulative and stratified antibiograms using non-parametric inferential statistics. Results The hospital-wide antibiogram under-estimated susceptibility rates in adult patients isolates (age group = 18-50 years) and over-estimated susceptibility rates in isolates from the paediatric patients and elderly. Paediatric isolates were found to be less susceptible to amikacin and imipenem, whereas isolates from elderly patients >50 years were less susceptible to ciprofloxacin. Statistically significant difference was seen in the susceptibility rates of OPD and IPD isolates of P. aeruginosa in the case of the paediatric age group. Susceptibility rates for all drugs were lower for isolates from inpatients than from outpatients. Conclusion Age and location associated differences in susceptibility rates have the potential to influence empirical antibiotic selection, which was shown in stratified antibiograms of P. aeruginosa that is obscured by hospital-wide antibiograms.