Fett William F
Food Safety Intervention Technologies Research Unit, Eastern Regional Research Center, Agricultural Research Service, US Department of Agriculture, Wyndmoor, Pennsylvania 19038, USA.
J Food Prot. 2006 Apr;69(4):719-28. doi: 10.4315/0362-028x-69.4.719.
Foodborne illness due to the consumption of contaminated raw or lightly cooked sprouts is a continuing food safety concern. In this study, we tested several plant-associated pseudomonads for their ability to inhibit the growth of Salmonella enterica both in vitro and in situ. An agar spot bioassay method was used with three different media. Only Pseudomonas fluorescens 2-79 produced clear zones of inhibition when tested against five serovars of S. enterica, and activity was dependent on media type and serovar. The antibiosis by derivative strains of P. fluorescens 2-79 defective in the production of phenazine-1-carboxylic acid and fluorescent siderophore was not reduced, indicating that these known antimicrobial metabolites were not responsible for the inhibition observed in our studies. However, mutants defective in the regulatory gene gacS (global antibiotic and cyanide control) were severely reduced in inhibitory activity. In tryptic soy broth, the control cultures of a cocktail of S. enterica strains reached approximately 10 log CFU/ml by 24 h but, when coinoculated with P. fluorescens 2-79, reached only approximately 5 log CFU/ml. The addition of P. fluorescens 2-79 to the seed soak water prior to the germination of alfalfa seed previously inoculated with a cocktail of S. enterica strains led to an average reduction of 5 log CFU/g at 6 days of sprouting without an adverse effect on sprout yield or appearance. Time course studies indicated that S. enterica outgrowth was controlled on days 1 through 6 of sprouting. Competitive exclusion as a potential food safety intervention for seed sprouts merits further study.
食用受污染的生豆芽或轻度烹饪的豆芽导致的食源性疾病一直是食品安全关注的问题。在本研究中，我们测试了几种与植物相关的假单胞菌在体外和原位抑制肠炎沙门氏菌生长的能力。使用琼脂斑点生物测定法，采用三种不同的培养基。当针对肠炎沙门氏菌的五个血清型进行测试时，只有荧光假单胞菌2-79产生了清晰的抑制圈，并且活性取决于培养基类型和血清型。荧光假单胞菌2-79的吩嗪-1-羧酸和荧光铁载体产生缺陷的衍生菌株的抗菌作用并未降低，表明这些已知的抗菌代谢产物与我们研究中观察到的抑制作用无关。然而，调节基因gacS（全局抗生素和氰化物控制）缺陷的突变体的抑制活性严重降低。在胰蛋白胨大豆肉汤中，肠炎沙门氏菌菌株混合物的对照培养物在24小时时达到约10 log CFU/ml，但与荧光假单胞菌2-79共同接种时，仅达到约5 log CFU/ml。在先前接种了肠炎沙门氏菌菌株混合物的苜蓿种子发芽前，将荧光假单胞菌2-79添加到种子浸泡水中，在发芽6天时平均降低了5 log CFU/g，且对豆芽产量或外观没有不利影响。时间进程研究表明，在发芽的第1至6天，肠炎沙门氏菌的生长受到控制。竞争排斥作为种子豆芽潜在的食品安全干预措施值得进一步研究。
