Campylobacter spp. are the second leading bacterial cause of food borne illness in the U.S.  New antimicrobials that prevent bacterial attachment may be effective for reducing Campylobacter.  Delmopinol hydrochloride (delmopinol) is a cationic surfactant that is effective for treating and preventing gingivitis and periodontitis.  This study evaluated the effectiveness of delmopinol for reducing attachment of Campylobacter jejuni to chicken, stainless steel and high-density polyethylene. Chicken pieces, steel and HDPE coupons were spot-inoculated with 0.1 mL of a Campylobacter jejuni culture.  After 10 min, samples were sprayed with 0.5% or 1.0% delmopinol, 0.01% sodium hypochlorite, or distilled water.  Contact times were 1, 10, or 20 min prior to rinsing with buffered peptone water. Rinses were serially diluted onto Campy Cefex Agar for enumeration.  For additional samples, solutions were applied first, followed by inoculation with C. jejuni after 10 min.  Cultures remained undisturbed for 1, 10, or 20 min.  Then samples were rinsed and plated as above. When C. jejuni was inoculated before treatments, 1% delmopinol application led to mean log reductions of 1.26, 3.70, and 3.72 log CFU/mL, greater than distilled water, for chicken, steel and HDPE respectively. When C. jejuni was inoculated after spray treatments, 1% delmopinol reduced C. jejuni by 2.72, 3.20, and 3.99 mean log CFU/mL more than distilled water for chicken, steel and HDPE respectively.  Application of 1% delmopinol, either before or after bacteria inoculation, resulted in a significantly (p<0.05) greater log reduction than 0.01% sodium hypochlorite or distilled water. Delmopinol may be a promising antimicrobial treatment. / Master of Science in Life Sciences

Since the surfaces of cantaloupes are highly rough or irregular, Salmonella enteric and other bacteria can easily attach to these surfaces and are difficult to remove. Cetylpyridinium chloride (CPC) is the active ingredient of some antiseptic oral mouth rinses and has a broad antimicrobial spectrum with a rapid bactericidal effect on Gram-positive pathogens. Delmopinol hydrochloride (delmopinol) is a cationic surfactant that is effective for treating and preventing gingivitis and periodontitis. The application of delmopinol or CPC to cantaloupe surfaces may be an alternative post harvest technique to reduce the frequency and level of Salmonella contamination. Cantaloupe (Athena and Hale's Best Jumbo (HBJ) cultivars) rind plugs were inoculated with a broth culture of Salmonella Michigan. After 15 min, plugs were sprayed with 10 ml of a 1% delmopinol solution, or a CPC solution (0.5 or 1.0%) or distilled water (Control), and held at 37 oC for 1 hr or 24 hr. For additional samples, the chemical treatments were applied 15 min before pathogen inoculation. Melon plugs were submerged in Butterfield's Phosphate Buffer, shaken, sonicated and solutions were enumerated on Tryptic Soy Agar. The texture quality and color of additional melon samples were evaluated after delmopinol or CPC spray treatments and storage at 4 oC. A 1.0% application of CPC reduced Salmonella levels up to 2.34 log CFU/ml (Athena) and 4.95 log CFU/ml (HBJ) in comparison to the control (p<0.01). A 1.0% delmopinol treatment reduced Salmonella levels as much as 3.1 log CFU/ml in comparison to the control (p<0.01) on both cultivars. In general, the log recovery of Salmonella on cantaloupes treated with delmopinol or CPC solutions, after 1 hr storage, was significantly lower (p<0.05) than the recovery from control cantaloupes, but Salmonella recovery was not significantly different after 24 hr. No significant differences were observed in the texture and color of melons treated with delmopinol or CPC after 14 days. A surface spray application of delmopinol hydrochloride or cetylpyridinium chloride could be an alternative antimicrobial post-harvest treatment that could make cantaloupes surfaces more susceptible to sanitizers or enhance physical removal of bacteria. / Ph. D.

Bacterial biofilms attached to food contact surfaces are an ongoing concern for the food industry due to the resistance of bacteria within biofilms to detergents and sanitizers. Within food manufacturing facilities, stainless steel is a common food-contact surface in which microbial cell attachment and biofilm formation may occur. Identifying methods to prevent and remove biofilms during standard cleaning and sanitation practices could prove useful, as mature biofilms can release planktonic cells into an aqueous environment, causing continual low-level contamination. Dental studies involving delmopinol hydrochloride, a cationic surfactant, have found a preventative and dissociating affect on biofilms, where food applications have scarcely been researched. This study demonstrates the prevention and removal of Listeria monocytogenes 1/2a and S. enterica Agona biofilms on stainless steel with pre- and post-exposures of delmopinol hydrochloride. Stainless steel blanks (#304, 16 gauge, 2cm x 2cm, finish #4) were submerged in a 0.2% or 0.5% delmopinol solution before or after biofilm formation. Treatment times were 1, 5 or 10 minutes, whereas controls were not exposed to the delmopinol solution. Disinfected stainless steel blanks were spot-inoculated with 20µL of a 10⁹ CFU/mL liquid culture, and pre-exposed blanks were additionally submerged in delmopinol and dried prior to inoculation. Biofilms were exclusively formed on the finished and inoculated side by placing the surface face-down on TSA. After cell attachment and biofilm development for 24 hours at 25°C, blanks were rinsed with phosphate buffer. Post-exposed blanks were submerged in 0.2% or 0.5% delmopinol for 1, 5 or 10 minutes before all blanks were individually vortexed for 90 seconds to dislodge films. Bacterial populations were determined by surface plating onto TSA followed by incubation at 32°C for L. monocytogenes and 37°C for S. Agona for 48 hours. Treatments were in-duplicate and repeated three times for each microorganism. Pre-exposure of 0.2% delmopinol resulted in a significant decrease in L. monocytogenes concentration at 1, 5 and 10 minute exposures (P < 0.05). Pre-exposures with the 0.5% solution had no significant effect on L. monocytogenes biofilm populations (P > 0.05), whereas all post-exposures lead to a significant decline in biofilm concentrations (P < 0.0001). Post-exposures of 10 minutes exhibited a mean log₁₀ reduction of 5.59 and 6.40 log₁₀ for 0.2% and 0.5% delmopinol solutions, respectively. For S. Agona, 0.2% pre-exposure resulted in no significant log10 reduction (P > 0.05), while the 10 minute 0.5% pre-exposure exhibited a minimal reduction in bacterial growth (P < 0.05). Post-exposures of 10 minutes exhibited a mean log10 reduction of 7.65 and 7.75 log10 for 0.2% and 0.5% delmopinol solutions, respectively. For L. monocytogenes and S. Agona, post-exposure to delmopinol hydrochloride caused a notable log10 reduction. The removal effect of delmopinol on biofilms is significantly greater the preventative effect. / Master of Science in Life Sciences