Antimicrobial-Resistant Escherichia coli from Environmental Waters in Northern Colorado

Table 1

Relative abundances of total detected bacteria and E. coli by water source and by ESBL and KPC production.

Source	Sampling events	Total detected bacteria (CFU/100 mL)			Escherichia coli (CFU/100 mL)
		All	ESBL	KPC	All	ESBL	KPC
Sewer water	6	2.1E + 08^b,c (2.8E + 08)	2.5E + 06^b,c (1.3E + 06)	3.2E + 06^b,c (1.5E + 06)	7.6E + 07^b,c (1.2E + 08)	3.1E + 05^b (2.6E + 05)	2.1E + 05 (2.1E + 05)
WWTP influent	3	3.5E + 08^d,e (3.2E + 08)	3.5E + 06^d,e (1.9E + 06)	3.6E + 06^d,e (1.3E + 06)	7.7E + 07^d,e (1.5E + 08)	2.3E + 05^d (1.1E + 05)	7.8E + 04 (7.0E + 04)
WWTP effluent	2	1.5E + 05^b,d (2.2E + 05)	1.4E + 03^b,d (1.4E+ 03)	1.6E + 02^b,d (1.3E + 02)	3.6E + 03^b,d (4.3E + 03)	100^d,b (102)	BDL
Surface water	6	2.1E + 04^c,e (3.8E + 04)	1.4E + 03^c,e (1.9E + 03)	5.8E + 02^c,e (5.5E + 02)	2.9E + 03^c,e (4.7E + 03)	500 (0)	BDL

Data represent colony counts collected during membrane filtration; all data are presented as mean (±standard deviation). Abundance was measured as colony-forming units/100 mL. Plates with counts between 15 and 300 total CFUs were considered for analysis. CFU = colony-forming unit. BDL = below detection limit. ESBL = extended-spectrum beta-lactamase. KPC = Klebsiella pneumoniae carbapenemase. WWTP = wastewater treatment plant. Statistical differences () are noted between water sources with the following letters: ^asewer water and WWTP influent, ^bsewer water and WWTP effluent, ^csewer water and surface water, ^dWWTP influent and WWTP effluent, and ^eWWTP influent and surface water.