Campylobacter in the context of "Oxidase test"

A microaerophile is a microorganism that requires environments containing lower levels of dioxygen than those present in the atmosphere (i.e. < 21% O₂; typically 2–10% O₂) for optimal growth. A more restrictive interpretation requires the microorganism to be obligate in this requirement. Many microaerophiles are also capnophiles, requiring an elevated concentration of carbon dioxide (e.g. 10% CO₂ in the case of Campylobacter species).

The original definition of a microaerophile has been criticized for being too restrictive and not accurate enough compared to similar categories. The broader term microaerobe has been coined to describe microbes able to respire oxygen "within microoxic environments by using high-affinity terminal oxidase".

Gastroenteritis, also known as infectious diarrhea, is an inflammation of the gastrointestinal tract including the stomach and intestine. Symptoms may include diarrhea, vomiting, and abdominal pain. Fever, lack of energy, and dehydration may also occur. This typically lasts less than two weeks. Although it is not related to influenza, in Canada and the United States it is often referred to as "stomach flu".

Gastroenteritis is usually caused by viruses; however, gut bacteria, parasites, and fungi can also cause gastroenteritis. In children, rotavirus is the most common cause of severe disease. In adults, norovirus and Campylobacter are common causes. Eating improperly prepared food, drinking contaminated water or close contact with a person who is infected can spread the disease. Treatment is generally the same with or without a definitive diagnosis, so testing to confirm is usually not needed.

Capnophiles are microorganisms that thrive in the presence of high concentrations of carbon dioxide (CO₂).

Some capnophiles may have a metabolic requirement for carbon dioxide, while others merely compete more successfully for resources under these conditions. The term is a generally descriptive one and has less relevance as a means of establishing a taxonomic or evolutionary relationship among organisms with this characteristic.

Travelers' diarrhea (TD) is a stomach and intestinal infection experienced during travel to a new location as a result of lack of immunity to local food-borne pathogens. TD is defined as the passage of unformed stool (one or more by some definitions, three or more by others) while traveling. It may be accompanied by abdominal cramps, nausea, fever, headache and bloating. Occasionally dysentery may occur. Most travelers recover within three to four days with little or no treatment. About 12% of people may have symptoms for a week.

Bacteria are responsible for more than half of cases, typically via foodborne illness and waterborne diseases. The bacteria enterotoxigenic Escherichia coli (ETEC) are typically the most common except in Southeast Asia, where Campylobacter is more prominent. About 10 to 20 percent of cases are due to norovirus. Protozoa such as Giardia may cause longer term disease. The risk is greatest in the first two weeks of travel and among young adults. People affected are more often from the developed world.