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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: Persistence of salmonella Typhimurium in Nopal

Authors
item Landa-Salgado, Patricia -
item Hernandez Anguiano, A -
item Vargas Hernandez, M -
item Eslava Campos, C -
item Chaidez Quiroz, C -
item Patel, Jitu

Submitted to: Revista Fitotecnia Mexicana
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 1, 2013
Publication Date: February 1, 2013
Citation: Landa-Salgado, P., Hernandez Anguiano, A.M., Vargas Hernandez, M., Eslava Campos, C., Chaidez Quiroz, C., Patel, J.R. 2013. Persistence of salmonella Typhimurium in Nopal. Revista Fitotecnia Mexicana. 36(2):147-153.

Interpretive Summary: The Nopal (paddle cactus) plant is a common and regular part of a variety of cuisine dishes in Mexico. Young cladode (pad) of nopal may be contaminated with Salmonella at the pre-harvest level. We evaluated persistence of Salmonella Typhimurium in nopal and in soil. Nopal plants and soil were inoculated with Salmonella and then evaluated for surviving population of Salmonella for 14 days. The persistence of Salmonella on nopal pad varied with physiological conditions. Salmonella were undetectable in secondary cladodes after 9 days; however, they persisted on mother cladodes and pre-cut cladodes for 14 days. Further, Salmonella contamination activated the defense response mechanism of nopal. A dark lesion at the inoculation site was observed in cladodes irrespective of their physiological conditions. Further, cladode dehydration and tissue detachment was observed in secondary cladodes. The adoption of Good Agricultural Practices (GAPs) to minimize Salmonella contamination will be helpful in reducing foodborne infections associated with nopal consumption. This information should be useful to other scientists.

Technical Abstract: Having documented information available on the capability of Salmonella to remain in the cladode tissue it is important to understand the role of nopal on the lifecycle of enteropathogenic bacteria in humans, as well as for management and control programs of theses pathogens in plants. Because of this, one of the objectives of this work was to evaluate the persistence of S. enterica serovar Typhimurium (S. Typhimurium) in nopal (Opuntia ficus-indica) and in the soil. Another objective was to determine if nopal plants respond to inoculations with the bacterium, and compare the response among cladodes with different physiological conditions (mother cladodes, secondary cladodes in planta, and precut cladodes). S. Typhimurium was detected in the soil and nopal tissue for up to 14 days. However, its persistence in the plant depended on the physiological condition of the tissue. In secondary cladodes in planta, the bacterium remained for 9 days, while in the mother cladodes and precut secondary cladodes it remained for 14 days. There were significant differences (a = 0.05) in the bacterial population due to the physiological condition of the cladode.In the tissue, S. Typhimurium caused dark lesions at the place of infiltration both on mother cladodes and on secondary cladodes in planta, as well as in precut secondary cladodes. However, these lesions were more intense in secondary cladodes in planta after 48 hours. Moreover, the bacterium caused dehydration symptoms and tissue detachment only in secondary cladodes. In absence of the bacterium, no responses were registered in the tissue. Symptoms of tissue darkening and dehydration, as well as the early definition of the lesion, registered in secondary cladodes in planta, indicated that S. Typhimurium has the capability of inducing a defense response in nopal.

Last Modified: 10/30/2014
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