Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/31/2008
Publication Date: 7/1/2008
Citation: Gallegos-Robles, M., Loredo, A., Ojeda, G., Vega, A., Chew, Y., Velarde, S., Fratamico, P.M. 2008. Identification of Salmonella Serotypes Isolated from Cantaloupe and Chile Pepper Production Systems in Mexico by PCR-Restriction Fragment Length Polymorphism. Journal of Food Protection. 71(11):2217-2222.
Interpretive Summary: The genus Salmonella consists of over 2700 members known as serotypes, and only a few serotypes are responsible for causing the majority of human diseases caused by this pathogen. Salmonella infection has been associated with the consumption of raw and undercooked poultry and other meat products; however, many outbreaks have also been associated with contaminated fresh fruits and vegetables. To develop strategies to control Salmonella contamination in fruits and vegetables, a thorough understanding of the prevalence and sources of this pathogen in produce production systems is needed. Furthermore, tests employing molecular tools can be useful in simplifying identification and serotyping of Salmonella strains isolated from various sources. A study was conducted to determine the prevalence of Salmonella species in cantaloupe and chile pepper production systems in Mexico. Salmonella was found on the surfaces of cantaloupes and peppers and in irrigation water. A method, known as PCR-RFLP, based on enzymatic digestion of a fragment of DNA from Salmonella was used to determine the serotypes of the strains that were obtained. The results showed that Salmonella Typhimurium was the only serotype found in the cantaloupe farms, whereas both Salmonella Typhimurium and Salmonella Enteritidis serotypes were found associated with the chile pepper farm. These are two major serotypes associated with animals and food and with human illness. This study demonstrates the utility of the PCR-RFLP technique for determining the serotypes of Salmonella isolates obtained from cantaloupe and chile pepper production systems.
Technical Abstract: A study was conducted in 2006 to determine the prevalence of Salmonella spp. in three cantaloupe farms in Matamoros, Coahuila, Mexico and one farm that cultivates chile peppers var Bell in Culiacán, Sinaloa, Mexico. Samples from cantaloupe farms consisted of cantaloupe rinses, irrigation water, water from furrows in the field, and workers’ hands, and from the chile pepper farm, they consisted of rinses of chile peppers obtained at the field, fruit rinses obtained at the packing house, and irrigation water. A total of 55 samples were obtained from both production systems. Twelve and 10 of the samples from the cantaloupe and chile pepper production systems, respectively tested positive for Salmonella. The difference between the proportion of positive samples from the cantaloupe production system (12/28 = 0.43) and the chile pepper production system (10/27 = 0.37) was not statistically significant (P>0.05). A PCR-RFLP typing method based on the fliC gene was used to determine the serotype of the isolates obtained. The PCR-RFLP results showed that S. Typhimurium was the only serotype found in the cantaloupe farms, whereas both S. Typhimurium and S. Enteritidis serotypes were found associated with the chile pepper farms. Results showed that 91 (20/22) and 9% (2/22) of the isolates from both agricultural systems matched with the S. Typhimurium and S. Enteritidis restriction profiles, respectively. This study demonstrates the utility of the PCR-RFLP technique for determining the serotypes of Salmonella isolates obtained from cantaloupe and chile pepper production systems.