Regional Differences in Carbapenem Non-Susceptibility in US Hospitals in 2015

Background: Carbapenem non-susceptibility (NS) in Gram-negative (GN) bacteria is recognized as a serious issue in the US, though regional data are limited.

Methods: Electronic data from a Becton, Dickinson & Company research database for 346 US hospitals were analyzed for the year 2015. All inpatient, non-duplicate GN isolates (first isolate of a species per 30 day period) from all sources (urine, skin, blood, intra-abdominal, respiratory, other), that were reported, were classified as carbapenem NS if intermediate or resistant to: a) imipenem or meropenem for Pseudomonas aeruginosa(PsA) or b) imipenem, meropenem, or ertapenem for Enterobacteriaceae. Geographic regions were as per National Healthcare Safety Network categories (Sievert 2013, ICHE). Regions 1, 7, and 8 were grouped as "other" due to the low number of hospitals (n=11). Pairwise comparisons between regions used the region with the lowest NS rate as the reference group.

Results: PsA, Klebsiella pneumoniae (KP), and Escherichia coli (EC) comprised the majority of tested isolates (162,710/206,907). The highest NS rates were in PsA, ranging from 10.2% (region 10) to 29.2% (region 2) (all regions 22.4%). KP NS rates ranged from 0.4% (“other”) to 16.8% (region 2) (all regions 5.4%). EC isolates were the most numerous though NS rates were low: 0.3% (range 0.1% – 0.4%).

US region (hospitals, n)	States/territories	Most frequent isolates
		P. aeruginosa		K. pneumoniae			E. coli
		Isolates, n	NS rate, %	Isolates, n	NS rate, %	Isolates, n		NS rate, %
2 (30)	NJ, NY, PR, VI	4095	29.2	3075	16.8	7727		0.4
3 (13)	DE, DC, MD, PA, VA, WV	1059	23.0	889	7.8	2615		0.2
4 (98)	AL, FL, GA, KY, MS, NC, SC, TN	11,681	20.9	10,373	2.6	27,347		0.3
5 (85)	IL, IN, MI, MN, OH, WI	8807	22.4	8365	7.5	24,624		0.3
6 (59)	AR, LA, NM, OK, TX	5699	21.8	5644	2.0	16,925		0.2
9 (28)	AZ, CA, HI, Pacific Islands	3530	24.9	2576	6.5	8329		0.4
10 (22)	AK, ID, OR, WA	699	10.2	757	0.8	2985		0.1
Other 1, 7, 8 (11)	All other	1006	16.9	909	0.4	2994		0.2
All regions (346)		36,576	22.4	32,588	5.4	93,546		0.3

Conclusion: Carbapenem NS is primarily observed in PsA in US hospitals. Of the most common Enterobacteriaceae, KP has the highest rates of NS. Regional differences are considerable; accordingly, clinicians should be aware of their local antibiogram and reporting patterns when creating treatment protocols.