Bach Susan J, Stanford Kim, McAllister Timothy A
Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, 4200 Highway 97, Summerland, BC, Canada V0H 1Z0.
FEMS Microbiol Lett. 2005 Nov 1;252(1):25-33. doi: 10.1016/j.femsle.2005.08.030.
The survival of Escherichia coli O157:H7 in feces from steers fed corn (CO) or barley (BA) was evaluated at -10, +4 and +22 degrees C. Fecal pats were inoculated with a four-strain mixture of nalidixic-acid resistant E. coli O157:H7 at two levels: 10(3) CFU g(-1) (low, L) and 105 CFU g(-1) (high, H). At -10 degrees C, duration of survival of E. coli O157:H7 was reduced (p < 0.05) in CO-L (35 days) compared to BA-L (49 days), likely due to the effects of fecal volatile fatty acids in combination with a fecal pH of <6.5. At 4 degrees C, E. coli O157:H7 was detected in BA-H, CO-H, CO-L and BA-L for 77, 77, 56 and 63 days, respectively, with no difference (p > 0.05) observed in the duration of survival or rate of decline of E. coli O157:H7 among treatments. Survival of E. coli O157:H7 was twice as likely (p < 0.05) at 22 degrees C than at 4 degrees C and -10 degrees C. While pH and dry matter content increased, and volatile fatty acid concentrations decreased over 84 days at all three temperatures, these changes were most pronounced at 22 degrees C. Survival of E. coli O157:H7 for extended periods of time in feces from both corn- and barley-fed animals was demonstrated, thus fecal material may serve as a vector for the transmission of the organism. The greater survival of E. coli O157:H7 at 22 degrees C suggests that temperature may play a role in the seasonality of transmission and prevalence of this bacterium in feedlot cattle. The reported greater prevalence of E. coli O157:H7 in cattle fed barley as compared to those fed corn does not appear to be related to elevated risk of transmission arising from differential survival of the bacterium in feces.
在-10℃、4℃和22℃条件下，评估了饲喂玉米（CO）或大麦（BA）的阉牛粪便中大肠杆菌O157:H7的存活情况。用耐萘啶酸的大肠杆菌O157:H7四菌株混合物以两种水平接种粪便堆：10³CFU g⁻¹（低，L）和10⁵CFU g⁻¹（高，H）。在-10℃时，与BA-L（49天）相比，CO-L中大肠杆菌O157:H7的存活时间缩短（p<0.05），这可能是由于粪便挥发性脂肪酸与pH<6.5的粪便共同作用的结果。在4℃时，在BA-H、CO-H、CO-L和BA-L中分别在77、77、56和63天检测到大肠杆菌O157:H7，各处理间大肠杆菌O157:H7的存活时间或下降速率无差异（p>0.05）。大肠杆菌O157:H7在22℃时存活的可能性是4℃和-10℃时的两倍（p<0.05）。虽然在所有三个温度下，pH和干物质含量在84天内增加，挥发性脂肪酸浓度降低，但这些变化在22℃时最为明显。已证明大肠杆菌O157:H7在饲喂玉米和大麦的动物粪便中均可长时间存活，因此粪便物质可能是该病菌传播的载体。大肠杆菌O157:H7在22℃时的更高存活率表明温度可能在育肥牛中该细菌传播的季节性和流行率中起作用。与饲喂玉米的牛相比，报道的饲喂大麦的牛中大肠杆菌O157:H7患病率更高，这似乎与该细菌在粪便中不同的存活情况导致的传播风险升高无关。
