Bell Rebecca L, Zheng Jie, Burrows Erik, Allard Sarah, Wang Charles Y, Keys Christine E, Melka David C, Strain Errol, Luo Yan, Allard Marc W, Rideout Steven, Brown Eric W
Division of Microbiology, Office of Regulatory Science, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration College Park, MD, USA.
Eastern Shore Agricultural Research and Extension Center, Virginia Tech Painter, VA, USA.
Front Microbiol. 2015 May 7;6:415. doi: 10.3389/fmicb.2015.00415. eCollection 2015.
Virginia is the third largest producer of fresh-market tomatoes in the United States. Tomatoes grown along the eastern shore of Virginia are implicated almost yearly in Salmonella illnesses. Traceback implicates contamination occurring in the pre-harvest environment. To get a better understanding of the ecological niches of Salmonella in the tomato agricultural environment, a 2-year study was undertaken at a regional agricultural research farm in Virginia. Environmental samples, including tomato (fruit, blossoms, and leaves), irrigation water, surface water and sediment, were collected over the growing season. These samples were analyzed for the presence of Salmonella using modified FDA-BAM methods. Molecular assays were used to screen the samples. Over 1500 samples were tested. Seventy-five samples tested positive for Salmonella yielding over 230 isolates. The most commonly isolated serovars were S. Newport and S. Javiana with pulsed-field gel electrophoresis yielding 39 different patterns. Genetic diversity was further underscored among many other serotypes, which showed multiple PFGE subtypes. Whole genome sequencing (WGS) of several S. Newport isolates collected in 2010 compared to clinical isolates associated with tomato consumption showed very few single nucleotide differences between environmental isolates and clinical isolates suggesting a source link to Salmonella contaminated tomatoes. Nearly all isolates collected during two growing seasons of surveillance were obtained from surface water and sediment sources pointing to these sites as long-term reservoirs for persistent and endemic contamination of this environment.
弗吉尼亚州是美国鲜食番茄的第三大生产地。弗吉尼亚州东海岸种植的番茄几乎每年都会引发沙门氏菌病疫情。溯源表明污染发生在收获前的环境中。为了更好地了解番茄种植环境中沙门氏菌的生态位，在弗吉尼亚州的一个区域农业研究农场开展了一项为期两年的研究。在生长季节收集了包括番茄（果实、花朵和叶子）、灌溉水、地表水和沉积物在内的环境样本。使用改良的美国食品药品监督管理局微生物分析手册（FDA - BAM）方法对这些样本进行沙门氏菌检测。采用分子检测方法对样本进行筛查。共检测了1500多个样本。75个样本沙门氏菌检测呈阳性，分离出230多个菌株。最常分离出的血清型是纽波特沙门氏菌和爪哇那沙门氏菌，脉冲场凝胶电泳显示出39种不同的图谱。在许多其他血清型中进一步凸显了遗传多样性，它们显示出多种PFGE亚型。对2010年收集的几株纽波特沙门氏菌分离株进行全基因组测序，并与因食用番茄而感染的临床分离株进行比较，结果表明环境分离株与临床分离株之间几乎没有单核苷酸差异，这表明沙门氏菌污染番茄存在源头联系。在两个生长季节的监测期间收集的几乎所有分离株均来自地表水和沉积物源，这表明这些地点是该环境中持续性和地方性污染的长期储存库。
