Secular trends in gram-negative resistance among urinary tract infection hospitalizations in the United States, 2000-2009

Abstract

Objective: Urinary tract infections (UTIs) are common among hospitalized patients. Selection of an appropriate antibiotic for this infection requires knowledge of both its general microbiology and the epidemiology of drug-resistant organisms. We sought to determine secular trends in UTI hospitalizations that involve gram-negative (GN) multidrug-resistant Pseudomonas aeruginosa (MDR-PA), extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (EC) and Klebsiella pneumoniae (KP), and carbapenem-resistant Enterobacteriaceae (CRE).

Design: Survey.

Patients: Patients with UTI in US hospitals between 2000 and 2009.

Methods: We first derived the total number of UTI hospitalizations in the United States from the Healthcare Cost and Utilization Project Nationwide Inpatient Sample database years 2000-2009. Based on a literature review, we then determined what proportion of all UTIs arise due to each of the organisms of interest, irrespective of resistance pattern. Finally, we assessed the prevalence of resistance within each pathogen based on the Eurofins Surveillance Network database 2000-2009. Susceptibility patterns served as phenotypic surrogates for resistance.

Results: Between 2000 and 2009, the frequency of UTI hospitalizations increased by approximately 50%, from 53 to 77 cases per 1,000 hospitalizations. Infections due to all GN bacteria followed a similar trajectory, whereas those caused by resistant GN pathogens increased by approximately 50% (MDR-PA) to approximately 300% (ESBL). CRE emerged and reached 0.5 cases per 1,000 hospitalizations in this 10-year period.

Conclusions: The epidemiology and microbiology of GN UTI hospitalizations has shifted over the past decade. The proportion of all hospitalizations involving this infection has climbed. Resistant GN bacteria are becoming more prevalent and are implicated in an increasing proportion of UTIs among hospitalized patients.