Maryland Institute for Applied Environmental Health, School of Public Health, University of Maryland, 2234P SPH Building, College Park, MD 20742, USA.
Environ Res. 2012 Apr;114:31-9. doi: 10.1016/j.envres.2012.02.005. Epub 2012 Mar 8.
Salmonella outbreaks associated with the consumption of raw tomatoes have been prevalent in recent years. However, sources of Salmonella contamination of tomatoes remain poorly understood. The objectives of this study were to identify ecological reservoirs of Salmonella on tomato farms, and to test antimicrobial susceptibilities of recovered Salmonella isolates. Fourteen Mid-Atlantic tomato farms in the U.S. were sampled in 2009 and 2010. Groundwater, irrigation pond water, pond sediment, irrigation ditch water, rhizosphere and irrigation ditch soil, leaves, tomatoes, and swabs of harvest bins and worker sanitary facilities were analyzed for Salmonella using standard culture methods and/or a flow-through immunocapture method. All presumptive Salmonella isolates (n=63) were confirmed using PCR and the Vitek(®) 2 Compact System, and serotyped using the Premi(®)Test Salmonella and a conventional serotyping method. Antimicrobial susceptibility testing was carried out using the Sensititre™ microbroth dilution system. Four of the 14 farms (29%) and 12 out of 1,091 samples (1.1%) were found to harbor Salmonella enterica subsp. enterica. Salmonella was isolated by the immunocapture method from soil, while the culture method recovered isolates from irrigation pond water and sediment, and irrigation ditch water. No Salmonella was detected on leaves or tomatoes. Multiple serotypes were identified from soil and water, four of which-S. Braenderup, S. Javiana, S. Newport and S. Typhimurium-have been previously implicated in Salmonella outbreaks associated with tomato consumption. Resistance to sulfisoxazole was prevalent and some resistance to ampicillin, cefoxitin, amoxicillin/clavulanic acid, and tetracycline was also observed. This study implicates irrigation water and soil as possible reservoirs of Salmonella on tomato farms and irrigation ditches as ephemeral habitats for Salmonella. The findings point to the potential for pre-harvest contamination of tomatoes from contaminated irrigation water or from soil or water splash from irrigation ditches onto low-lying portions of tomato plants.
近年来，与食用生番茄有关的沙门氏菌疫情时有发生。然而，人们对番茄受沙门氏菌污染的源头仍知之甚少。本研究的目的是确定番茄种植场中沙门氏菌的生态储库，并测试回收的沙门氏菌分离株的抗菌药敏性。2009 年和 2010 年，对美国 14 个中大西洋番茄种植场进行了采样。使用标准培养方法和/或流动免疫捕获法，对地下水、灌溉池塘水、池塘底泥、灌溉沟渠水、根际和灌溉沟渠土壤、叶片、番茄以及收获箱和工人卫生设施的拭子进行沙门氏菌分析。所有疑似沙门氏菌分离株（n=63）均采用 PCR 和 Vitek(®)2 Compact 系统确认，并采用 Premi(®)Test Salmonella 和传统血清分型方法进行血清分型。采用 Sensititre™微量肉汤稀释系统进行抗菌药敏试验。14 个农场中有 4 个（29%）和 1091 个样本中的 12 个（1.1%）发现含有肠炎沙门氏菌亚种。免疫捕获法从土壤中分离出沙门氏菌，而培养法从灌溉池塘水和底泥以及灌溉沟渠水中回收分离株。叶片或番茄上未检测到沙门氏菌。从土壤和水中鉴定出多种血清型，其中 4 种血清型-S. Braenderup、S. Javiana、S. Newport 和 S. Typhimurium-以前曾与与食用番茄有关的沙门氏菌疫情有关。磺胺甲噁唑耐药普遍存在，对氨苄西林、头孢西丁、阿莫西林/克拉维酸和四环素也有一定耐药性。本研究表明，灌溉水和土壤可能是番茄种植场中沙门氏菌的潜在储库，灌溉沟渠可能是沙门氏菌的短暂栖息地。研究结果表明，番茄可能受到污染灌溉水或来自土壤或水溅到番茄植株低洼部分的污染。
