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U.S. Department of Health and Human Services


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List of Terms: O

Return to Comprehensive List of Terms


Did You Know?

Many foodborne illness outbreaks are not reported because people often feel like they have the flu, and they often do not know that their illness was caused by harmful bacteria or other pathogens in food.


> Outbreak  
An incident in which 2 or more cases of a similar illness result from eating the same food.

Food Safety Implication: Foodborne illness outbreaks are caused by foods that are contaminated internally or that become contaminated during harvesting, processing, or preparation. When there is an outbreak of foodborne illness, public health scientists use epidemiological, microbiological, and trace-back technologies to control the outbreak and remove the food from the distribution channels.

For example, PulseNet is a national network of public health laboratories that performs DNA "fingerprinting" on bacteria. This network helps to characterize foodborne bacteria and establishes links between related cases over a wide geographical area. This allows for the identification and removal of foods that cause multiple cases of illness from the marketplace. (Also see PulseNet.)


> Oxygen Tension
The measure of the amount of oxygen that is available for an organism to use in growth.

Food Safety Implication: Aerobic organisms are those organisms that can grow in the presence of O2. Some, in fact, will not grow without it. Anaerobic organisms are those organisms that grow in the absence of O2. In fact, some are killed by the presence of O2.

Foods are usually contaminated or contain mixed populations of microorganisms. As each population grows, a few species will predominate. As these microbial populations use up their food, they begin to die off, and a second microbial species will succeed the first. This process is called ecological succession. Many times, a population of aerobic organisms will use up all the available oxygen that the succeeding population will need, and thus will select a more anaerobic succeeding species.