Microbial Ecology and Foodborne Disease Emerging Microbiological Food Safety Issues: Implications for Control in the 21st Century

The complexity of the pre-harvest,harvest, and post-harvest environments makes it impossible to control all potential sources of microbial contamination. Efforts at prevention and control are implemented throughout the food production and processing system. Researchers are continually searching for a better understanding of the pathogens and their interaction with the environment, leading to improved control technologies. But at the same time, the pathogens continue to evolve, and human actions sometimes drive that evolution. Even small environmental changes can have unforeseen or even unforeseeable impact on microbial populations. Improved understanding of these complex factors provides insight into pathogen evolution and opens the door to new and improved prevention and control methods.

Pre-Harvest Environment

Efforts to minimize microbial contamination of food begin in the pre-harvest environment. Raw ingredients are one way in which pathogens are introduced into the food supply. Unfortunately, pathogen control in the production agriculture is often difficult. The widespread occurrence and use of animal manure as fertilizer is a growing concern, because it can spread pathogens to water, soil, and crops. Contaminated water also has tremendous potential to spread pathogens. Globalization of the world’s food supply has contributed to changing patterns of food consumption and foodborne illness. Global sourcing provides economic benefits and a wider selection for consumers that improves nutrition worldwide. However, in terms of disease control programs, globalization reduces traditional geographic barriers to emerging as well as traditional pathogens.

Harvest Environment

The harvest environment is relatively commodity specific, because the methods used and harvest locations depend on the commodity in question. The harvest environment is especially important for foods such as fruits and vegetables that undergo minimal additional processing prior to consumption.

Post-Harvest Environment

Microbiological food safety issues in the post-harvest environment have the potential to affect many different foods as the food moves through processing into the distribution and retail sectors. Also, at the processing stage, ingredients from many different commodity sectors may be combined into a single product. As ingredients are combined, the physical characteristics of the food change, and its microbiological profile is altered.

The microbiological controls applied in the post-harvest environment are often designed to intentionally stress the microorganisms present in the food. These stresses may be designed to be lethal on their own or in combination. Environmental conditions also may be modified to limit microbial growth, through such techniques as drying or refrigeration. Each of these stresses has an impact on the microbial population in the food.

As the scientific understanding of foodborne pathogens has become more sophisticated, so too have the control methods. These control efforts are one of many driving forces in pathogen evolution, and as such, their impact on the virulence and survival of foodborne pathogens must be fully considered. Scientists study the effect of processing technologies and other changes to the microbial environment to evaluate the effectiveness of control technologies and also the potential that control efforts will drive pathogen evolution. For example, a food may be rinsed with an organic acid to kill pathogens on the surface. However, if pathogens survive, they may become acid-tolerant and better able to survive passage through the human stomach to cause illness in the small intestine. Although much of the emphasis in microbiological methods development traditionally has been on pathogen detection and identification in food, it is critical to develop better ways of monitoring pathogen survival in the food processing environment, so that the factors that influence food contamination may be understood and controlled.

New processing and packaging technologies offer the potential for continued improvement in the sensory quality of foods, extended shelf life, and enhanced microbiological safety. However, these new processes and packaging technologies may change the microbial ecology, resulting in potential positive and negative effects that must be assessed along the entire food chain. Even an apparently insignificant change in the microbial environment can trigger a food safety concern because of the complexity of the microbial environment and the interrelationship of various factors.

Recognizing that food safety is a fundamental and continuing issue, the Institute of Food Technologists commissioned an expert panel to review the available scientific literature related to emerging microbiological food safety issues. The panel’s report is divided into seven sections: Introduction, Pathogenicity, Human Hosts, Microbial Ecology, Application of Science to Food Safety Management, Next Steps, and Conclusions. Copies of the report are available at www.ift.org. Founded in 1939, IFT is a 28,000 member nonprofit scientific society for food science and technology.