Antimicrobial Effects of Quillaja saponariaExtract Against Escherichia coliO157: H7 and the Emerging Non‐O157 Shiga Toxin‐Producing E. coli

• Autores: Fatih Özogul, Doris H. D'Souza
• Localización: Journal of food science, ISSN 0022-1147, Vol. 82, Nº 5, 2017, págs. 1171-1177
• Idioma: inglés
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• Resumen

  • Natural alternate methods to control the spread of Shiga toxin‐producing Escherichia coli (STEC) are important to prevent foodborne outbreaks. Quillaja saponariaaqueous bark extracts (QE), cleared by the U.S. Food and Drug Administration as a natural flavorant, contain bioactive polyphenols, tannins, and tri‐terpenoid saponins with anti‐inflammatory and antimicrobial activity. The objective of this study was to determine the effects of commercial QEagainst E. coliO157:H7 and non‐O157 strains over 16 h at 37 °C and RT. Overnight cultures of 4 E. coliO157:H7 strains and 6 non‐O157 STECs in Tryptic Soy Broth (TSB) were washed and resuspended in phosphate‐buffered saline (PBS, pH 7.2), and treated with QE and controls including citric acid (pH 3.75), sodium benzoate (0.1% w/w), acidified sodium benzoate (pH 3.75) or PBS for 6 h or 16 h. Recovered bacteria were enumerated after plating on Tryptic Soy Agar, from duplicate treatments, replicated thrice and the data were statistically analyzed. The 4 QE‐treated E. coliO157:H7 strains from initial ∼7.5 log CFU had remaining counts between 6.79 and 3.5 log CFU after 16 h at RT. QE‐treated non‐O157 STECs showed lower reductions with remaining counts ranging from 6.81 to 4.55 log CFU after 16 h at RT.  Incubation at 37 °C caused reduction to nondetectable levels within 1 h, without any significant reduction in controls. Scanning electron microscopy studies revealed damaged cell membranes of treated bacteria after 1 h at 37 °C. QE shows potential to control the spread of STECs, and further research in model food systems is needed. Quillaja saponariaaqueous bark extracts (QE) have U.S. Food and Drug Administration clearance as natural flavoring substances. The objective of this study was to determine the effects of commercial QEagainst E. coliO157:H7 and the emerging non‐O157 shigatoxin‐producing E. coli(STEC) strains over 16 h at 37 °C and RT. The 4 E. coliO157:H7 strains and non‐O157 STECs treated with QE at RT showed significant reductions after 16 h. Incubation temperature of 37 °C caused reduction to nondetectable levels within 1 h, without any significant reduction in the untreated controls. Scanning electron microscopy studies revealed damaged cell membranes of treated bacterial cells after 1 h at 37 °C. QE shows potential to control the spread of STECs.