We identified all hospitalizations carrying a diagnosis of MRSA, Clostridium difficile
–associated disease (CDAD), vancomycin-resistant enterococcus (VRE), Pseudomonas aeruginosa,
infections for 2000–2005 from the National Inpatient Sample data. These data are available on the Healthcare Costs and Utilization Project net [HCUPnet] website, administered by the Agency for Healthcare Research and Quality (8
). We used the corresponding diagnosis codes from the International Classification of Diseases, 9th revision, Clinical Modification (Appendix Table
). Because few reports of vancomycin-resistant Staphylococcus aureus
), we assumed that most cases with the code V09.8 represented VRE infections. We limited hospitalizations in which Candida
organisms had been identified to deep-seated infections, including candidiasis of the lung, disseminated candidiasis, candidal endocarditis, meningitis, esophagitis, and enteritis. The numbers of discharges per year for infections associated with each organism and in aggregate were stratified by census region. We obtained regional estimates of all US hospitalizations in the corresponding years from the HCUPNet (8
), and censal and intercensal data on the US population for 2000–2005 from the US Census Bureau. We calculated region-specific hospitalization incidence rates associated with the resistant pathogens. Because large numbers would predispose the study to type I error, we did not perform formal significance testing; rather, we focused on clinical and policy-relevant trends.
The overall volume of resistant infections increased by 89.6% from year 2000 through 2005 (). As a proportion of the total volume growth, the increases across regions were comparable. The southern region had the highest raw volume of resistant infections for the study period (2000, 37.3%; 2005, 39.1%). The West had the smallest contribution in 2000 (19.0%) and 2005 (19.5%). However, the Northeast had the highest relative incidence per 1,000 hospitalizations with 14.00 in year 2000; its incidence of 19.98 in 2005, however, was lower than that in the South, 20.76/1,000 (). Regional disparities in the population-based incidence of hospitalizations with resistant organisms also occurred (). Thus, the incidence in the Northeast was not only the highest for 5 of the 6 years examined, but compared to that seen in the lowest-incidence region, the West, was higher by as much as 41.9% in 2003. This gap shrank in 2004 and 2005 to 29.9% and 27.7%, respectively.
Volume, incidence of, and hospitalizations for infections with resistant organisms in the United States, by census region, 2000–2005
When the incidences of individual component infections were examined, several patterns emerged. While the Northeast led other regions in the incidence of CDAD hospitalizations over the entire period examined (, panel A), the South exhibited the highest population incidence of MRSA and Pseudomonas hospitalizations. Although temporal patterns of regional population incidence varied somewhat for hospitalizations in which VRE and Candida spp. infections were diagnosed, by year 2005 the Northeast emerged as the region with the highest incidence of VRE, while the South had the highest incidence of Candida spp. hospitalizations. The lowest incidence of VRE hospitalizations was consistently seen in the southern region in each of the studied years. The incidence of hospitalizations with pseudomonal infections remained relatively stable regionally over time (, panels B, C, D).
Figure Population incidence of component resistant infections in the United States, by census region, 2000–2005. A) Clostridium difficile–associated disease; B) methicillin-resistant Staphylococcus aureus; C) vancomycin-resistant enterococcus; (more ...)