TABLE 3.

Distribution of antimicrobial susceptibility clusters of fecal commensal E. coli isolates from calves^a

Cluster	No. of isolates in calves at age:
	1 day				14 days				28 days
	Group 1	Group 2	Group 3	Group 4	Group 1	Group 2	Group 3	Group 4	Group 1	Group 2	Group 3	Group 4
A	56	63	59	78	21	16	5	0	14	25	20	0
B	3	5	6	3	0	5	15	0	0	0	18	0
C	0	1	0	0	1	1	0	0	0	0	0	0
D	1	1	0	0	1	2	1	0	1	0	0	0
E	11	3	0	4	14	6	6	0	16	1	4	2
F	2	0	0	1	1	2	3	0	0	3	4	0
G	0	4	2	0	0	1	0	0	5	1	0	0
H	0	0	0	0	1	0	0	0	3	0	0	0
I	3	1	5	0	1	7	2	0	3	5	5	3
J	0	0	0	0	0	0	0	0	3	3	1	1
K	0	0	0	0	0	3	0	1	0	2	0	0
L	2	2	1	0	3	6	4	0	1	6	1	0
M	1	0	0	2	8	7	5	0	4	8	0	0
N	0	0	0	0	0	8	0	0	0	0	0	0
O	0	1	2	0	0	0	3	3	1	0	0	4
P	0	0	1	0	0	0	0	6	0	3	2	0
Q	0	0	0	0	0	0	11	5	0	0	0	0
R	0	0	0	0	1	0	0	0	0	0	1	5
S	0	0	0	4	3	6	13	1	0	2	3	3
T	0	1	3	0	0	2	7	3	0	0	1	8
U	0	0	0	0	6	0	4	0	0	0	0	0
V	0	0	1	0	5	0	1	21	0	0	10	4
W	0	0	0	0	0	0	4	50	0	0	3	48
X	0	0	0	0	0	0	0	0	0	0	0	3
Sum	79	82	80	92	66	72	84	90	51	59	73	81

^aThe influence of antimicrobials in the milk replacer and as therapy on the antimicrobial susceptibility in E. coli was evaluated. Group 1, no antimicrobial therapy and housed isolated from other study groups; group 2, no antimicrobial therapy and housed within the calf ranch; group 3, antimicrobial therapy available and housed within the calf ranch; group 4, antimicrobial therapy available, housed within the calf ranch, and received milk replacer medicated with antibiotics.