用于识别粪便来源的四种主要方法都没有检测生物标志物随季节的变化。在大肠杆菌群体或采样点中，生物标记物出现的差异很少受到关注。目前，农场废物收集方法的生物标志物差异、畜群规模或动物密度的影响被忽略。这项工作包括对来自美国农场的样本进行测试，以确定来自7个州的猪群和4个州的牛群中大肠杆菌群体中毒素基因生物标记物的致死性。这些农场样本还用于测试基于聚合酶链反应（PCR）的人类、牛和猪生物标记物方法的可靠性，并通过检测来自相应肠毒素基因STh、STII和LTIA的物种特异性序列来确定粪便来源。建立了一种五滤池三稀释法来估计毒素阳性大肠杆菌的数量。 大肠杆菌总数中的大肠杆菌。包括10个参考文献和表格。

None of the four main methods used to identify fecal sources has examinedvariation of the biomarkers over season. Differences among the biomarkers'occurrence in the E. coli population or amongst sampling sites have receivedlittle attention. Biomarker variation across waste collection methods on farms,the effects of herd size, or animal density are presently ignored. This workincluded the testing of samples from the farms in the US to determine theendemicity of the toxin gene biomarkers in E. coli populations among swine herdsfrom 7 states and cattle herds from 4 states. These farm samples were also usedto test the reliability of the human, cattle, and swine biomarker methods whichare polymerase chain reaction (PCR)-based and determine the fecal source bydetecting a species-specific sequence from the respective enterotoxin genes, STh,STII, and LTIIa. A five filter three dilution method was developed to estimatethe number of toxin positive E. coli within the total E. coli population. Includes 10 references, tables.