Richards H A, Pérez-Conesa D, Doane C A, Gillespie B E, Mount J R, Oliver S P, Pangloli P, Draughon F A
Food Science and Technology Department, The University of Tennessee, Knoxville, Tennessee 37996, USA.
Foodborne Pathog Dis. 2006 Fall;3(3):259-65. doi: 10.1089/fpd.2006.3.259.
Many of the current studies on the genetic diversity of Escherichia coli O157:H7 have focused on pathogenic clinical, veterinary, or food isolates. These studies did not explore the diversity of the larger population in the farm environment. Research on selected farm isolates address this wider diversity but have typically been limited to a specific geographic locale or farm type, thus giving limited insight into the greater diversity across geographic regions and varied environments. The objective of this study was to evaluate a diverse population of E. coli O157:H7 collected from a variety of locations and farm environments. Eighty-eight isolates were collected from four farm types (swine, dairy, beef, and poultry) across the southeastern and western United States. Eighteen farms were sampled every 3 months over a period of 24 months. Isolates were analyzed by ribotyping and pulsed field gel electrophoresis (PFGE). Real-time PCR was used to determine the presence or absence of key pathogenic genes (stx1, stx2, and eae). The data indicate a significant amount of genetic diversity, however, ribotype analysis revealed meaningful clusters within the larger population. These groupings were consistent with PFGE analysis. Most of these isolates were clustered by location (i.e. from the same state or region) or farm type. Of the isolates in these clusters, most did not contain pathogenic genes. Of notable interest is a single group in which the majority of isolates, collected from four of the five states sampled, contained at least one stx gene and the eae gene suggesting the existence of a specific pathogenic cluster. These data suggest that, while there is notable diversity within the broader E. coli O157:H7 population, pathogenic isolates may be limited to a subset of strains within the population.
目前许多关于大肠杆菌O157:H7基因多样性的研究都集中在致病性临床、兽医或食品分离株上。这些研究没有探讨农场环境中更大群体的多样性。对选定农场分离株的研究涉及了更广泛的多样性，但通常仅限于特定的地理区域或农场类型，因此对跨地理区域和不同环境的更大多样性的了解有限。本研究的目的是评估从各种地点和农场环境中收集的不同大肠杆菌O157:H7群体。从美国东南部和西部的四种农场类型（猪、奶牛、肉牛和家禽）收集了88株分离株。在24个月的时间里，每3个月对18个农场进行采样。通过核糖体分型和脉冲场凝胶电泳（PFGE）对分离株进行分析。使用实时PCR来确定关键致病基因（stx1、stx2和eae）的存在与否。数据表明存在大量的基因多样性，然而，核糖体分型分析揭示了在更大群体中有意义的聚类。这些分组与PFGE分析一致。这些分离株大多按地点（即来自同一州或地区）或农场类型聚类。在这些聚类中的分离株中，大多数不含有致病基因。值得注意的是，有一个单一的组，其中从采样的五个州中的四个州收集的大多数分离株都含有至少一个stx基因和eae基因，这表明存在一个特定的致病聚类。这些数据表明，虽然在更广泛的大肠杆菌O157:H7群体中存在显著的多样性，但致病分离株可能仅限于该群体中的一部分菌株。
