348

Abstract

Introduction: Administration of initially appropriate antimicrobial therapy represents a key determinant of outcome in critically ill patients with severe infection. However, the prevalence of antimicrobial resistance complicates the process of antibiotic selection. Recent efforts to address resistance have focused on prevention and antimicrobial stewardship. It is unclear if resistance patterns have changed in light of these initiatives. More specifically, Pseudomonas aeruginosa (PA), a common and concerning pathogen in pneumonia, is frequently resistant to multiple classes of antibiotic agents. Hypothesis: We hypothesized that the proportion of pneumonia cases with multi-drug resistant PA (MDR-PA) has remained essentially stable. Methods: To derive national estimates over time of MDR-PA pneumonia we used multiple data sources. We examined Eurofins’ TSN database 2000-2009 to explore the proportion of all PA in pneumonia that is MDR. We defined MDR-PA as any isolate resistant to?3 drug classes. The proportion of all hospitalized pneumonia that is due to PA was extracted from published literature. The total volume of hospitalizations with pneumonia was computed from the HCUP-NIS database 2000-2009. The proportion of all pneumonia hospitalizations that are MDR-PA was calculated using the HCUP-NIS data as the denominator. Results: Among the 187,343 PA pneumonia specimens available in the TSN database, 41,180 (22.0%) were MDR-PA. The proportion of all PA that was MDR-PA fluctuated between 19.2% (95% CI 18.6%-19.7%) in 2000 and 21.7% (95% CI 21.0%-22.5%) in 2009, with the highest proportion seen in 2007 at 24.2% (95% CI 23.6%-24.9%) (p for linear trend 0.435). Between 2000 and 2009 the annual incidence of MDR-PA pneumonia hospitalizations rose from 2.07 (95% CI 1.93-2.20) to 2.79 (95% CI 2.59-3.01) cases per 1,000 hospitalizations (p for linear trend 0.002). This was a function of the growth of the overall incidence of pneumonia hospitalization, which climbed from 57.00 (95% CI 55.01-58.98) to 68.02 (95% CI 65.36-70.69) cases per 1,000 hospitalizations (p for linear trend <0.001). Conclusions: Although the total volume of MDR-PA pneumonias has increased, this appears to reflect an increase in the volume of pneumonia hospitalizations. The proportion (~1 in 5) of all PA that is MDR has remained high but stable.