National Prevalence of Multidrug-Resistance (MDR) in Enterobacteriaceae (ENT) in the Ambulatory and Acute Care Settings in the United States in 2015

Background:Infections caused by resistant Gram-negative bacteria are a serious global public health concern. The purpose of this study was to estimate the national prevalence of MDR ENT events in the acute care and ambulatory settings based on a large database from Becton Dickinson & Company.

Methods: Susceptibility data from non-duplicate E. coli, K. pneumoniae, P. mirabilis, E. aerogenes, E. cloacae, S. marcescens, C. freundii, & M. morganii and were identified from 346 hospitals nationwide. ENT isolates were characterized as MDR per NHSN definitions. Organisms were classified into ambulatory, admission, and hospital-onset (HO) setting based on collection time. All data were consolidated into CMS National Hospital Data Provider IDs. The raking method was applied per CMS national hospital distribution by location, teaching status, urban/rural status, and bed size to project the national prevalence estimates.

Results: Of 904,446 isolates tested, 41,457 were MDR ENT. The national projected MDR ENT events were 379,163 in the HO, ambulatory and acute care settings (table below). The MDR ENT rates were highest in the HO, followed by admission and ambulatory setting. National Projections for MDR ENT for each region were: ambulatory (3.1, 3.3, 4.6 & 3.3%), admission (5.8, 6.4, 6.2 & 6.2%) and HO (7.6, 10.2, 9.2 & 9.0%) for the Midwest, Northeast (NE), South, and West regions, respectively. 

	Observed Events (346 hospitals)			National Projection
Period Tested	Isolates tested	Confirmed MDR EB	% MDR ENT	Isolates tested	MDR EB Events	% MDR ENT
Ambulatory	683,143	25,305	3.7	6,538,605	241,058	3.7
Admission	119,842	7,225	6.0	1,025,088	62,465	6.1
Hospital-onset	101,461	8,927	8.8	853,616	75,641	8.9
Total	904,446	41,457	4.6	8,417,309	379,163	4.5
Regions
Midwest	244,752	9,060	3.7	2,636,407	102,174	3.9
NE	138,490	6,180	4.5	1,331,936	59,703	4.5
South	381,550	19,898	5.2	2,968,073	156,355	5.3
West	139,654	6,319	4.5	1,480,893	60,932	4.1
Total	904,446	41,457	4.6	8,417,309	379,163	4.5

Conclusion: Although the highest prevalence for MDR ENT events was in the HO setting, over 90% of MDR ENT events occurred in the ambulatory and admission settings. Overall prevalence of MDR ENT was highest in the South region, but the NE has the highest projected prevalence for the admission and HO periods.