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Campylobacter are gram negative, flagellate, microaerophilic curved rods that include both pathogenic and commensal organisms of the gastrointestinal tract. They are nonfermentative and nonoxidative, deriving energy from amino acids and Krebs cycle intermediates. Although originally classified with the genus Vibrio, they were reclassified in 1973 based on differences in their cell walls and DNA content. The most important of these species is C. jejuni.
Epidemiology: Based on data reported from hospitals, the CDC estimates the annual incidence of C. jejuni infection to be 5-6 per 100,000 people. However, infection may be underreported as some laboratories do not routinely culture this organism and some patients do not seek medical attention. Population based studies estimate the annual incidence of C. jejuni infection to be as high as approximately 1000 per 100,000 people. Campylobacter jejuni causes between 3.2% and 6.1% of diarrheal disease, compared to between 2.1% and 3.6% for Salmonella.
There is a bimodal age distribution, with a peak for infants and a second peak for young adults (15 to 30 years). Infection is highest in the summer months. Sporadic cases may result from contaminated foods, raw milk, or contact with animals. Rare cases of person to person transmission have been reported. Outbreaks have been associated with improperly pasteurized milk and contaminated water.
Pathogenesis: The infective dose varies from as few as 500 organisms to more than 1 billion. Virulence factors include enterotoxin production, tissue invasiveness, and flagellar motility. Immunohistochemical and ultrastructural evidence of invasion of the colonic mucosa have been identified, as have an increased number of IgA and IgM secreting plasma cells in the mucosa of infected patient
Clinical Features: C. jejuni enterocolitis is most commonly a self-limited diarrheal illness similar to the enteritis caused by Salmonella or Shigella species. The diarrhea frequently starts watery but becomes bloody as the disease progresses. Other common symptoms include abdominal pain, malaise, fever, anorexia, nausea, vomiting, and grossly bloody stools. The abdominal pain may mimic acute appendicitis, but C. jejuni is rarely a cause of appendicitis. The usual incubation period is 1 to 3 days. The peak of the illness is 1 to 2 days, and resolution occurs over a week. Excretion of the organism may continue for four weeks beyond resolution. Extraintestinal infection is uncommon in immunocompetent individuals but may manifest as cholecystitis, pancreatitis, or bacteremia. In immunocompromised individuals, C. jejuni bacteremia is more frequent and severe. There are now numerous reports of Guillain-Barre syndrome following C. jejuni infection, although the pathogenesis remains unclear.
Diagnosis: Although a presumptive diagnosis can be made either by gram stain or by observing the darting organisms on phase contrast microscopy, the gold standard is culture. Campylobacter require selective blood or charcoal based media and proper atmosphere (5% oxygen, 10% carbon dioxide and 85% nitrogen). Alternatively, a membrane filtration technique with nonselective blood agar media can be employed. Campylobacter jejuni can be distinguished from other species by growth at 42 C and by its ability to hydrolyze hippurate to benzoic acid and glycine.
Therapy: The mainstay of treatment of diarrheal illness remains fluid and electrolyte replacement. When antibiotic therapy is indicated, as when there are greater than eight stools a day, worsening or persistent symptoms for more than one week, or high fevers, erythromycin is the first drug of choice. Resistance has been reported in 0.5% to 8.4% of isolates, and alternative agents include ciprofloxacin, gentamicin, doxycycline, and tetracycline.
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