National Prevalence of Extended Spectrum Beta-lactamase Producing Enterobacteriaceae (ESBL) in the Ambulatory and Acute Care Settings in the United States in 2015

Background: In 2013 the CDC classified infections caused by ESBL organisms as a serious threat. The purpose of this study was to estimate the national prevalence of ESBL events in outpatient and hospitalized patients based on the incidence of ESBL episodes in the Becton Dickinson research database.

Methods: Susceptibility data from non-duplicate organisms including E. coli, K. pneumoniae, and P. mirabilis were collected from 346 hospitals. ESBL was identified per NHSN definitions. Organisms were classified into ambulatory, admission, and hospital-onset (HO) periods 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 820,017 isolates tested, 56,718 were ESBL and the national projected ESBL events were 517,384 (see Table). The ESBL rates were highest in the HO period, followed by admission and ambulatory. Approximately 66% of all ESBL events occurred in the ambulatory settings. National Projections for ESBLs for each region were: ambulatory (4.7, 6.3, 6.3 & 5.6%), admission (8.6, 10.7, 9.0 & 8.9%) and HO periods (11.3, 16.6, 13.2 & 13.4%) for the Midwest, Northeast (NE), South and West regions, respectively.

	Observed Events (346 hospitals)			National Projection
Period Tested	Isolates tested	Confirmed ESBL	% ESBL	Isolates tested	ESBL Events	% ESBL
Ambulatory	631,846	36,086	5.7	6,058,591	341,955	5.6
Admission	105,846	9,693	9.2	907,674	82,717	9.1
HO	82,325	10,939	13.3	697,570	92,712	13.3
Total	820,017	56,718	6.9	7,663,836	517,384	6.8
Regions
Midwest	222,311	12,161	5.5	2,401,980	137,340	5.7
NE	125,175	9,727	7.8	1,208,894	95,351	7.9
South	344,377	26,047	7.6	2,689,175	195,007	7.3
West	128,154	8,783	6.9	1,363,786	89,686	6.6
Total	820,017	56,718	6.9	7,663,836	517,384	6.8

Conclusion: These data estimate that national hospital onset ESBL rates in 2015 were higher than previously reported. Although the highest prevalence of ESBL events occurred in the HO period, ESBL events were highest in frequency in the ambulatory period. The highest rates of ESBL infections were in the NE and South regions among all periods tested.