Assessment of a food microbiology senior undergraduate course as a potential food safety distance education course for poultry science majors.

Distance education courses have become popular due to the increased number of commuter students as well as people already in the workforce who need further education for advancement within their careers. A graduate-level Web-based course entitled Special Topics-Poultry Food Safety Microbiology was developed from an existing senior undergraduate advanced food microbiology course in the Poultry Science Department at Texas A&M University. Conversion of standard lecture material into a distance education course can provide unique challenges to maintain comparable course content in an asynchronous manner. The overall objective for this course was to examine bacterial activities including ecology in food, animals, raw and processed meat, eggs, and human pathogenesis. Students were surveyed at the end of the class and the majority agreed that they would be willing to take the course as an online course, although they were not willing to pay an extra fee for an online course. The majority of students used the online version of the course as a supplement to the classroom rather than as a substitute.

Effects of Maillard reaction products on hilA expression in Salmonella typhimurium.

Salmonella is a foodborne pathogen causing severe gastroenteritis. Three types of Maillard reaction products (MRP) generated by heat sterilization of D-glucose and L-lysine, L-histidine, and L-arginine were studied at 2 different levels of supplementation (0.5% and 1.0%) for their influence on growth and virulence of Salmonella. Two methods, namely, real-time polymerase chain reaction (RT-PCR) and a beta-galactosidase gene fusion assay, were used to determine the expression of hilA, a regulatory gene for Salmonella pathogenicity. Neither the type of MRP nor their quantities up to 1.0% affected the growth rates of S. Typhimurium EE658 (P > 0.05). When determined by beta-galactosidase assay, lysine MRP in both levels of supplementation were not found to have any effect on the hilA expression compared to the control. The addition of histidine and arginine MRP to M9 media (0.5%) increased by 2-fold hilA induction and up to 6-fold at the higher level (1%) supplementation of these compounds. Although somewhat inconsistent, RT-PCR analyses of hilA expression confirmed the greater induction effect of arginine MRP on hilA compared to lysine MRP. In contrast to beta-galactosidase assay results, however, lysine MRP were found to increase hilA expression compared to the control in both supplementation levels in all trials. The potential of MRP serving as a bacterial virulence modulator may be a factor to be considered in food thermal processing when assessing Salmonella risk for causing foodborne disease.

Growth and genetic responses of Salmonella Typhimurium to pH-shifts in an anaerobic continuous culture.

Salmonella infection of chickens that leads to potential human foodborne salmonellosis continues to be a concern. Changes in the pH of poultry gastrointestinal tract could influence Salmonella growth and virulence response. In the current study, growth responses of a chicken isolate Salmonella enterica serovar Typhimurium (ST) to three incremental pH-shifts (6.17-7.35) in continuous cultures (CC) were evaluated. The expression of rpoS and hilA was determined by real time-polymerase chain reaction (RT-PCR) as well. Increases in pH resulted in higher cell protein concentrations, glucose disappearance, and glucose and ATP yields. Although with some inconsistency between the two trials, the data indicated that the ammonia release into media was favored by low pH. The pH shifts did not significantly affect acetate biosynthesis. No consistent trends of pH influence on propionate and butyrate production could be detected. In all three pH shifts, relative expression of hilA was dominant at 0h which represented CC steady state. In pH shift 7.35-6.86 (Trial 1), the relative expression of rpoS at time 0 and 1h were over five-fold higher than after 3 and 6h of growth. Overall, the results suggest that ST physiology is altered by changes in pH, which could be determinant factors for ST survival in the poultry gastrointestinal ecosystems.

Alternatives to antibiotics: chemical and physical antimicrobial interventions and foodborne pathogen response.

Successful control of foodborne pathogens requires placement of chemical and physical hurdles in the preharvest and postharvest food production sectors. Pathogens may also encounter indigenous antimicrobials in foods including certain botanical compounds that have historically been used for flavor enhancement as well as preservation. Chemical additives have traditionally included organic acids to control microbial contamination in foods and feeds. However, there is some concern that continuous application of certain chemical antimicrobials can lead to a buildup of microbial resistance. This creates problems if foodborne pathogens survive and develop resistance to a variety of environmental stressors encountered in pre- and postharvest animal production. To expand the diversity of potential antimicrobials that have practical application to food animal production requires exploring the interaction between the food matrix and foodborne pathogens. There is potential for isolating antimicrobial compounds that exhibit mechanisms unrelated to conventional antimicrobial compounds. However, understanding the potential for novel antimicrobial compounds in foods and feeds will require the physiological examination of foodborne pathogen response under experimental conditions comparable to the environment where the pathogen is most likely to occur. Research on foodborne Salmonella pathogenesis is extensive and should provide a model for detailed examination of the factors that influence antimicrobial effectiveness. Analysis of pathogen response to antimicrobials could yield clues for optimizing hurdle technologies to more effectively exploit vulnerabilities of Salmonella and other foodborne pathogens when administering antimicrobials during food and feed production.