Isolation and Antimicrobial Susceptibility Profile of Escherichia coli O157 : H7 from Raw Milk of Dairy Cattle in Holeta District, Central Ethiopia

Table 2

Association of risk factors with the occurrence of E. coli O157 : H7 in the study area.

Variables	Category	No. examined	Positive	Ch-square (X^2)	value
Herd size	<10	114	5 (12.5%)	63.242	0.0001
	10–42	67	15 (37.5%)
	≥42	29	20 (50%)
Type of floor	Good concrete	68	4 (10%)	11.304	0.001
	Bad concrete	100	17 (42.5%)
	Soil	42	19 (47.5%)
Parity	1–3	159	35 (87.5%)	4.078	0.044
	4–6	46	5 (12.5%)
	>6	5	0 (0%)
Milking type	Hand	181	35 (87.5%)	0.071	0.0001
	Machine	29	5 (12.5%)
Body condition	Poor	57	22 (55%)	19.555	0.0001
	Moderate	130	16 (40%)
	Good	23	2 (5%)
Age in years	3–6	114	33 (82.5%)	15.918	0.0001
	6–9	62	5 (12.5%)
	≥9	34	2 (5%)
Farm hygiene	Poor	129	35 (87.5%)	14.175	0.0001
	Good	81	5 (12.5%)
Udder lesion	Yes	49	20 (50%)	19.642	0.0001
	No	161	20 (50%)
Udder hygiene	Washing/drying	161	3 (7.5%)	6.925	0.007
	Washing only	49	37 (92.5%)
Milk yield	Low	60	4 (10%)	25.002	0.852
	Medium	89	31 (77.5%)
	High	61	5 (12.5%)
Type of farm	Intensive	61	30 (75%)	51.262	0.0001
	Semi-intensive	130	10 (25%)
	Extensive	19	0 (0%)