Facultad de Ciencias Biológicas, Universidad Autónoma de Nuevo León, Apdo. Postal 124-F, San Nicolás, N.L., 66451, Mexico.
Division of Microbiology, Food and Drug Administration, College Park, MD, USA.
Food Microbiol. 2016 Oct;59:124-32. doi: 10.1016/j.fm.2016.06.001. Epub 2016 Jun 4.
The purpose of this study was to determine the effects of plant products on the growth, swarming motility, biofilm formation and virulence gene expression in enterohemorrhagic Escherichia coli O157:H7 and enteroaggregative E. coli strain 042 and a strain of O104:H4 serotype. Extracts of Lippia graveolens and Haematoxylon brassiletto, and carvacrol, brazilin were tested by an antimicrobial microdilution method using citral and rifaximin as controls. All products showed bactericidal activity with minimal bactericidal concentrations ranging from 0.08 to 8.1 mg/ml. Swarming motility was determined in soft LB agar. Most compounds reduced swarming motility by 7%-100%; except carvacrol which promoted motility in two strains. Biofilm formation studies were done in microtiter plates. Rifaximin inhibited growth and reduced biofilm formation, but various concentrations of other compounds actually induced biofilm formation. Real time PCR showed that most compounds decreased stx2 expression. The expression of pic and rpoS in E. coli 042 were suppressed but in E. coli O104:H4 they varied depending on compounds. In conclusion, these extracts affect E. coli growth, swarming motility and virulence gene expression. Although these compounds were bactericidal for pathogenic E. coli, sublethal concentrations had varied effects on phenotypic and genotypic traits, and some increased virulence gene expression.
本研究旨在确定植物产物对产志贺毒素和聚集性大肠杆菌 O157:H7 及 O104:H4 血清型菌株 042 生长、群集运动、生物膜形成和毒力基因表达的影响。采用柠檬酸和利福昔明作为对照，用抗菌微量稀释法测试了 Lippia graveolens 和 Haematoxylon brassiletto 的提取物以及香芹酚、巴西苏木素。所有产物均表现出杀菌活性，最小杀菌浓度范围为 0.08 至 8.1mg/ml。在软 LB 琼脂中测定群集运动。大多数化合物使运动性降低 7%-100%；除香芹酚外，它还促进了两种菌株的运动性。在微量滴定板上进行生物膜形成研究。利福昔明抑制生长并减少生物膜形成，但其他化合物的各种浓度实际上诱导了生物膜形成。实时 PCR 显示，大多数化合物降低了 stx2 的表达。pic 和 rpoS 在大肠杆菌 042 中的表达受到抑制，但在大肠杆菌 O104:H4 中，它们的表达因化合物而异。总之，这些提取物影响大肠杆菌的生长、群集运动和毒力基因表达。尽管这些化合物对致病性大肠杆菌具有杀菌作用，但亚致死浓度对表型和基因型特征有不同的影响，一些化合物增加了毒力基因的表达。
