Campylobacter jejuni (juh-JUNE-eye) is considered one of the most important from both a microbiological and public health perspective. Campylobacter jejuni is a gram-negative, microaerophilic, thermophilic rod that grows best at 42°C (107°F) and low oxygen concentrations. These characteristics are adaptations for growth in its normal habitat—the intestines of warm-blooded birds and mammals.
In the United States, these bacteria are the most common cause of bacterial foodborne illness, ahead of Salmonella—the second most common cause.
Although most cases of Campylobacter infection in humans are sporadic, a substantial number of outbreaks—30 outbreaks by one report, and 50 by another—have been linked to the consumption of unpasteurized (raw) milk. Raw milk is presumed to be contaminated by bovine feces; however, direct contamination of milk also occurs.
Most retail chicken is contaminated with C. jejuni; one study reported an isolation rate of 98% for retail chicken meat. C. jejuni counts often exceed 103 per 100 g. Skin and giblets have particularly high levels of contamination. In one study, 12% of raw milk samples from dairy farms in eastern Tennessee were contaminated with C. jejuni.
Campylobacters are also found in red meat. In one study, C. jejuni was present in 5% of raw ground beef and in 40% of veal specimens.
Most Campylobacter infections in humans are caused by the consumption of contaminated food or water.  Direct contact with infected animals, including pets, is also a well-documented means of disease-transmission.
The amount of time from infection to the onset of symptoms—typically referred to as the incubation period—can vary to a significant degree.
Campylobacteriosis symptoms can range from diarrhea and lethargy that lasts a day to severe diarrhea and abdominal pain (and occasionally fever) that lasts for several weeks. Diarrhea and abdominal pain are the most common symptoms, and most cases are mild.
Complications can include septicemia (bacterial pathogens in the blood, also known as bacteremia), meningitis, inflammation of the gall bladder (cholecystitis), urinary tract infections, and appendicitis.
A sizeable percentage of persons who suffer Campylobacter infections develop Guillain-Barre Syndrome, which causes neuromuscular paralysis. Over time, the paralysis is to some extent typically reversible; nonetheless, approximately 20% of patients with GBS are left disabled, and approximately 5% die.
Campylobacter jejuni grows poorly on properly refrigerated foods but does survive refrigeration and will grow if contaminated foods are left out at room temperature. The bacterium is sensitive to heat and other common disinfection procedures; pasteurization of milk, adequate cooking of meat and poultry, and chlorination or ozonation of water will destroy this organism. Infection control measures at all stages of food processing may help to decrease the incidence of Campylobacter infections, but the single most important and reliable step is to adequately cook all poultry products.
Most cases of Campylobacteriosis are sporadic or involve small family groups, although some common-source outbreaks involving many people have been traced to contaminated water or milk. Other sources of Campylobacter include children prior to toilet training, especially in childcare settings , and intimate contact with other infected individuals. C. jejuni is commonly present in the gastrointestinal tract of healthy cattle, pigs, chickens, turkeys, ducks, and geese, and direct animal exposure can lead to infection. Pets that may carry Campylobacter include birds, cats, dogs, hamsters, and turtles. The organism is also occasionally isolated from streams, lakes and ponds.