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United States Department of Agriculture

Agricultural Research Service

Research Project: MICROBIAL ECOLOGY AND SAFETY OF FRESH PRODUCE

Location: Environmental Microbial and Food Safety Laboratory

Title: Defense response in Nopal Cladodes infiltrated with Salmonella Typhimurium

Authors
item Landa, Salgado -
item Hernandez, Anguiano -
item Vargas, Hernandez -
item Eslava, Campos -
item Chaidez, Quiroz -
item PATEL, JITU

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: September 19, 2011
Publication Date: October 5, 2011
Citation: Landa, S., Hernandez, A., Vargas, H., Eslava, C., Chaidez, Q., Patel, J.R. 2011. Defense response in Nopal Cladodes infiltrated with Salmonella Typhimurium. Meeting Proceedings. p. 126-129.

Interpretive Summary: Foodborne outbreaks associated with fresh produce have increased in recent years. Pre-harvest contamination of fresh produce via irrigation water, soil, or other animal vectors may be responsible for many of these outbreaks. We evaluated defense response of nopal plants (a type of cactus) when contaminated with Salmonella in internal tissues of leaves (mother and secondary leaves on the plants, and precut secondary leaves). Samples were evaluated every day for 2 weeks for Salmonella populations and visual changes (intense darkening) as a defense response. The infiltration of S. Typhimurium in nopal leaves induced a defense response which was characterized by the intense darkening of inoculated tissues. Plant defense response was observed on secondary leaves on the plant during 48-96h post inoculation. Visual changes were confirmed by the significantly lower recovery of Salmonella populations on secondary leaves on the plant as compared to recovery of Salmonella in mother and precut secondary leaves. Further studies on biochemical and structural defense responses will be helpful to select nopal cultivars resistant to contamination by Salmonella.

Technical Abstract: Foodborne outbreaks associated with fresh produce have increased in recent years. Pre-harvest contamination of fresh produce via irrigation water, soil, or other animal vectors may be responsible for many of these outbreaks. We evaluated defense response of nopal plants when contaminated in internal tissues of cladodes. A 300 µl bacterial suspension containing 8 log CFU/ml Salmonella Typhimurium was injected in mother cladodes and secondary cladodes on the plant, and on precut secondary cladodes. Nopal cladodes injected with buffered peptone water (0.1%) served as control. Samples were evaluated every day for 2 weeks for Salmonella populations and visual changes (intense darkening) as a defense response. Presumptive positive Salmonella colonies were confirmed by the PCR assay. The infiltration of S. Typhimurium in nopal cladodes induced a defense response which was characterized by the intense darkening of inoculated tissues. Plant defense response was observed on secondary cladodes on the plant during 48-96h post inoculation. Visual changes were confirmed by the significantly lower recovery of Salmonella populations on secondary cladodes on the plant (1.42 log CFU/g) compared to recovery of Salmonella in mother cladodes (3.27 log CFU/g) and precut secondary cladodes (4.0 log CFU/g). Further studies on biochemical and structural defense responses will be helpful to select nopal cultivars resistant to contamination by Salmonella.

Last Modified: 8/19/2014
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