Table 1.

Antibiotic resistance genes detected in cultured bacteria and class 1 integron gene cassettes recovered from suspended floc across four variably impacted freshwater systems

Resistance	Gene(s)	Detectiona
		Hamilton		Toronto		Guelph		Coldspring		Total
		C	I	C	I	C	I	C	I	C	I
Aminoglycoside transferase	aac(3)Ia		+		+		+			3	10
	aac(3)IVa				+
	aac(6′)Ib		+
	aadA1 like	+	+
	aadA2 like		+
	aadA4 like		+		+
	ant(2″)Ia		+
	strB	+				+
Beta-lactamase (class A)b	blaCTX-M-1		+		+					3	5
	blaCTX-M-9		+
	blaLEN-1								+
	blaSHV	+
	blaTEM-1	+	+					+
Beta-lactamase (class D)	blaOXA-2		+	+	+					1	5
	blaOXA-7		+		+
	blaOXA-9				+
Beta-lactamase (class C)	blaACC-1				+					10	5
	blaACC-2							+
	blaACT-1	+	+	+		+		+
	blaCMY	+		+				+
	blaFOX			+
	blaMOX		+		+				+
	blaMOX-CMY							+
Chloramphenicol efflux pump	cmlA1 like		+
Chloramphenicol acetyltransferase	catB8		+
Erythromycin esterase	ereB		+	+	+
DNA gyrase protection protein (quinolone)	qnrB				+
	qnrS			+
Modified dihydropteroate synthase (sulfonamide)	sul1	+
	sul2		+						+
Streptogramin acetyltransferase	vatE		+
Tetracycline efflux pump	tetA	+								4	2
	tetC		+
	tetD			+
	tetE	+		+			+
Modified dihydrofolate reductase (trimethoprim)	dfr12			+						3	4
	dfrA1	+
	dfrA7		+				+
	dfrA15			+
	dfrA17		+				+
Total		10	21	10	11	2	4	5	3

^aC, culture-based detection method (combined results for pooled isolates from each type of culture medium); I, integron-based detection method; +, gene or group of gene variants was detected. The shading indicates detection of a gene or related sequence by single-gene PCR and sequencing.

^bBeta-lactamase class follows the Ambler classification system.