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United States Department of Agriculture

Agricultural Research Service

Research Project: VALIDATION OF THE EFFECT OF INTERVENTIONS AND PROCESSES ON PERSISTENCE OF PATHOGENS ON FOODS Title: Biofilm formation and antimicrobial resistance of Salmonella spp. isolated from nopal stems and water and soil samples

Authors
item Anguiano, Hernandez -
item Salgado, P. -
item DE Los Santos, A.A. -
item Campos, C. -
item Porto-Fett, Anna
item Luchansky, John

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: November 2, 2009
Publication Date: November 4, 2009
Citation: Anguiano, H., Salgado, P., De Los Santos, A., Campos, C.E., Porto Fett, A.C., Luchansky, J.B. 2009. Biofilm formation and antimicrobial resistance of Salmonella spp. isolated from nopal stems and water and soil samples. [abstract]. National Meeting of Food Microbiology, Hygience and Food Toxicology and XI International Meeting of Food Safety. p.1.

Technical Abstract: Nopal is a native cactus specie [Opuntia ficus-indica (L.) MILL (Cactaceae)] of appreciable economic importance in Mexico. This plant or its by-products are typically ingested fresh as a salad or processed into juice or yogurt, but it can also be used as a dietary supplement or be formulated into cosmetics. Because of its widespread production and consumption/uses, it was of interest to determine the association, if any, of target pathogens, such as Salmonella spp., with fresh cactus stems and associated soil and water samples. We determined that the prevalence of Salmonella spp. associated with nopal was at 67.6% (23 of 34 samples tested positive; 12 of 18 positive samples from nopal stems, 7 of 8 positive samples from surrounding soil, and 4 of 8 positive samples from pond/irrigation water). The isolates displayed 2 serotypes, namely S. Typhimurium and S. javiana, and 3 pulsotypes, namely pulsotype I (4 isolates from nopal leaves and 2 from soil), pulsotype II (2 isolates from soil), and pulsotype III (2 from water and 6 from nopal leaves). These data suggested that nopal could become contaminated with Salmonella from either water and/or surrounding soil and thus serve as a vehicle for transmission to humans. Thus, it was of further interest to investigate the antimicrobial susceptibility of these isolates and to chronicle their ability to form biofilms. Regarding the latter, although all strains displayed the ability to form biofilms in vitro, there were significant differences in their abilities to do so. Surprisingly, almost 70% of the 16 strains tested were sensitive to all 16 antimicrobials evaluated using the Vitek-60 automated method. However, the resistant strains were generally resistant to multiple antimicrobials, particularly to beta-lactams. There was no discernible correlation between the ability to form a biofilm and the susceptibility of a given strain to the antimicrobials tested. These data represent the first to establish the capacity for Salmonella isolated from nopal to form biofilms and/or to show resistance to antimicrobials, both of which are characteristics of concern from a public health perspective for people who may consume fresh nopal.

Last Modified: 12/22/2014