Members of the genus are curved, spiral, or S-shaped organisms that microscopically resemble vibrios (Figure 1). A single, polar flagellum provides the organism with its characteristic darting motility. Somatic, flagellar, and capsular antigens all contribute to the numerous serotypes. Most Campylobacter are microaerophilic (that is, they require oxygen but at lower concentrations than that found in air). Members of this genus use a respiratory pathway and do not ferment carbohydrates. Campylobacter infect the intestine and can cause ulcerative, inflammatory lesions in the jejunum, ileum, or colon. Bacteremia may occur.

Fig1. Micrograph showing the S-shaped cells of Campylobacter jejuni.

A. Epidemiology

Campylobacter are widely distributed in nature as commensals of many different vertebrate species, including mammals and fowl, both wild and domestic. These serve as reservoirs of infection. Campylobacter are transmitted to humans primarily via the fecal–oral route through direct contact, exposure to contaminated meat (especially poultry), or contaminated water supplies.

 B. Pathogenesis and clinical significance

Campylobacter may cause both intestinal and extraintestinal disease. The characteristics of some common forms of bacterial food borne illness are shown in Figure 2. [Note: Food infection should be distinguished from food poisoning. Food infections (like Campylobacter) have longer incubation periods and require colonization by the bacterium. Food poisonings have shorter incubation periods and only require ingestion of the toxin.] C. jejuni typically causes an acute enteritis in otherwise healthy individuals following a 1- to 7-day incubation. The disease lasts days to several weeks and, generally, is self-limiting. Symptoms may be both systemic (fever, headache, myalgia) and intestinal (abdominal cramping and diarrhea, which may or may not be bloody). Campylobacter jejuni is a cause of both traveler’s diarrhea and pseudoappendicitis (symptoms simulating appendicitis without inflammation of the appendix). Bacteremia (often transient) may occur, most often in infants and older adults. Sustained bacteremia usually reflects host compromise. Complications include septic abortion, reactive arthritis, and Guillain-Barré syndrome. Important virulence factors include a cytotoxin that may be involved in inflammatory colitis and an enterotoxin (related to cholera toxin) that results in increased adenylyl cyclase activity and, therefore, electrolyte and fluid imbalance. Campylobacter is currently one of the leading causes of foodborne disease in the United States.

Fig2. Characteristics of common forms of bacterial foodborne illness.

C. Laboratory identification

Campylobacter can be isolated from feces using special selective media and microaerophilic conditions. Because of their small size, these organisms are not retained by bacteriologic filters that hold back most other bacteria. Thus, filtration of the fecal suspension may enhance recovery rate. Presumptive diagnosis can be made on the basis of finding curved organisms with rapid, darting motility in a wet mount of feces.

D. Treatment and prevention

 Diarrhea should be treated symptomatically with fluid and electrolyte replacement. For patients with more severe symptoms (for example, high fever, bloody diarrhea, worsening illness, or illness of more than 1 week’s duration), antibiotics should be administered. For C. jejuni, ciprofloxacin is the drug of choice, but other antibiotics are also effective (Figure 3). For Campylobacter fetus, ampicillin or third-generation cephalosporins are effective. Thorough cooking of potentially contaminated foods (for example, poultry) and pasteurization of milk and milk products are essential to prevention of campylobacteriosis. Also, surfaces used to prepare raw meat or poultry should be disinfected before using them for uncooked food such as salads.

Fig3. Summary of Campylobacter disease. 1 Indicates first-line drugs.