6th Annual Judith Ramaley Celebration of Research and Creative Scholarship
|
Poster #121 Incubation of Salmonella enteritis on dog food causes elongation of the cells
Phyllis A. Wirs and Veranja M. Liyanarachchi
Faculty Mentor: Nicole Aulik
The Gram-negative, invasive bacteria, Salmonella, continues to cause approximately 1.4 million cases of food related illnesses in the United States yearly leading to increased standards for public health and safety. Salmonella enteria subtype typhi causes typhoid fever that can be contracted through food and water contaminated with the feces. Salmonella enteritis is more distinctly linked with food poisoning after the ingestion of contaminated food with high concentrations of the bacteria. In 2006, more than 600 people across 47 states became ill from Salmonella-contaminated peanut butter. The salty environment produced by the peanut butter allows for filamentation of the Salmonella. This cause of elongation proves to be more resistant when passing through the stomach acid unlike normal structured Salmonella where many die under the acidic conditions. Formation of filaments appears to be associated with food borne pathogens, but it is unknown if this response is a survival technique or consequence of stress. More recently, human infections have been connected to Salmonella-contaminated dry dog and cat food. This outbreak was the first ever documented human illness linked to dry dog and cat food. Overall, this raises concern that contamination of pet products could be an under recognized source of human infections. Here, we used Salmonella enteritis strain E.40 to examine the structure of the Salmonella cells incubated on two different forms of dog food. One form is the standard (uncoated) dog food, while the other contains a probiotic on the surface (coated) that is predicted to prevent the colonization of Salmonella on the dog food surface. We observed Salmonella enteritis E.40 elongated on the coated dog food, but interestingly we did not observe elongation on the uncoated dog food. Scanning electron microscopy preparation of the Salmonella incubated on dog food was modified for this experiment and images were acquired on the Feico Phenom scanning electron microscope (SEM). The bacteria was first be grown under normal conditions and 7% sodium chloride conditions and then each was incubated for 24 hours on either the uncoated and coated dog food. The dog food was then fixed using and dehydrated with alcohol. Dehydration is further continued with the method of critical point drying that replaces water in the biological tissue with carbon dioxide to reduce the distortion of structure and morphology of the bacteria followed by gold sputtering the samples. This technique creates a thin layer of gold on the surface to allow for the visibility of Salmonella. We observed the elongation of Salmonella enteritis E.40 on the coated dog food regardless of what sodium chloride concentration the bacteria was incubated in prior to the incubation with the dog food. Interestingly, elongation was not observed when Salmonella cells were incubated with the prebiotic-coated dog food regardless of the concentration of sodium chloride. These data provide information that will be useful when devising dog food preparation and ingredients, which could limit the ability of Salmonella to elongate and become more resistant to stomach acid. |
|