What is Campylobacter?

Definition

Campylobacter is a slender, curved-rod, gram-negative bacterium. The genus Campylobacter was first proposed in 1963, at which time it included only C. fetus and C. bululus (later renamed C. sputorum). Campylobacter, the leading cause of bacterial gastroenteritis worldwide, has a corkscrew appearance. The pathogen propels itself with one or two flagella, depending on the subspecies. It thrives best in a nonacidic environment that is 3 to 5 percent oxygen and 2 to 10 percent carbon dioxide. It is sometimes found in nonchlorinated bodies of water, such as ponds and streams.

The primary source of
Campylobacter infection, or campylobacteriosis, in humans is C. jejuni, which accounts for about 90 percent of all Campylobacter infections worldwide and up to 99 percent of infections in the United States. One of the highest rates of Campylobacter infection is seen in New Zealand, with 158.6 cases per 100,000 people in 2012, compared to a far lower rate of 14.3 per 100,000 people in the United States in the same year. Even this high rate represents a marked decrease from 2006, which saw a record 383.5 cases per 100,000. The reasons for New Zealand's high rate of infection are unknown.

Humans are infected through the consumption of unpasteurized milk, contaminated water, or contaminated food, such as raw or undercooked meat, especially poultry. They may also be infected via physical contact with fecal material expelled from infected humans or animals.

It is estimated that about two million people experience symptomatic Campylobacter infections each year in the United States. The incidence of such infections is as much as six times greater in rural areas. This higher incidence may occur because people in rural locations are believed to be more likely to drink unpasteurized (raw) milk than are persons in urban settings.

Natural Habitat and Features

Campylobacter colonizes the intestinal tract, the urogenital tract, or the oral cavity of healthy and sick animals, particularly chickens. It is also found in the intestinal tract of humans. C. jejuni is found in human and bovine (cow) feces, while C. coli is commonly found in the feces of pigs, humans, and chickens and in contaminated water. C. helveticus is found in the feces of cats and dogs.

The acidity of the human stomach kills most ingested Campylobacter, but some of the bacteria survive and attach themselves to the intestinal epithelial cells or the mucus on these cells. They then reproduce and proliferate within the intestines. Some people do not react symptomatically to this colonization, while others develop severe diarrhea. The diarrhea may be caused by an inflammatory response that occurs in the intestine as a result of the bacterial presence, or it may result from toxins that are produced by Campylobacter, which affect fluid resorption and cause diarrhea. In most cases, Campylobacter remains in the intestine of humans; rarely, it migrates to the bloodstream or to the lymphatic system. Such a migration is unusual in persons with normal immune systems.

Pathogenicity and Clinical Significance

Campylobacter infection has an incubation period of two to five days and lasts up to ten days. It is believed that fewer than five hundred organisms are required to cause an infection in the host. This is equivalent to about one drop of juice from an infected chicken.

An estimated 1 in 1,000 persons who are infected with Campylobacter develop Guillain-Barré syndrome (GBS), a neurological disorder and a leading cause of acute paralysis in the United States. Most infected persons recover in six to twelve months, but some never recover. According to the Centers for Disease Control and Prevention (CDC), up to 40 percent of all cases of GBS in the United States may be caused by infection with Campylobacter. When it occurs, GBS develops within two to four weeks after infection.

Persons with the acquired immunodeficiency syndrome
(AIDS) have an incidence of Campylobacter
that is about forty times greater than those without AIDS. Some persons without
AIDS have an immune deficiency in immunoglobulin A (IgA), thus increasing their
risk for infection with Campylobacter. Breast-fed babies have a
reduced risk for infection with Campylobacter, probably because
of the lactating woman’s transfer of maternal substances, particularly secretory IgA.

Drug Susceptibility

An increasing worldwide resistance of the Campylobacter pathogen to fluoroquinolone drugs has been noted since the late 1990s. Largely responsible for this resistance is the treatment of animals with fluoroquinolones to promote their growth. As a result, erythromycin (for children) and tetracycline (for adults) are now the recommended treatment drugs for campylobacteriosis. There is some resistance to erythromycin, but it is much lower than the resistance to fluoroquinolones such as ciprofloxacin. Newer macrolide antibiotics, such as azithromycin and clarithromycin, are also effective.

Some studies have shown that Campylobacter infections acquired during travel are more resistant to antibiotics than those acquired at home. For example, in one study in the Netherlands, resistance to fluoroquinolone antibiotics was 54 percent in travel-related infections, while the rate of resistance was a significantly lower 33 percent in infections in the study subject’s native area.

Bibliography

Alfredson, David A., and Victoria Korolik. “Antibiotic Resistance and Resistance Mechanisms in Campylobacter jejuni and Campylobacter coli.” FEMS Microbiology Letters 277.2 (2007): 123–32. Academic Search Complete. Web. 29 Dec. 2015.

“Campylobacter: Technical Information.” Centers for Disease Control and Prevention. Dept. of Health and Human Services, 18 Apr. 2013. Web. 29 Dec. 2015.

Janssen, Riny, et al. “Host-Pathogen Interactions in Campylobacter Infections: The Host Perspective.” Clinical Microbiology Reviews 21.3 (2008): 505–18. Web. 29 Dec. 2015.

Lopez, Liza, et al. Annual Report Concerning Foodborne Disease in New Zealand, 2012. Wellington: Ministry for Primary Industries, 2013. Ministry for Primary Industries. Web. 29 Dec. 2015.

Minocha, Anil, and Christine Adamec. The Encyclopedia of the Digestive System and Digestive Disorders. 2nd ed. New York: Facts on File, 2011. Print.

Nachamkin, Irving, Christine M. Szymanski, and Martin J. Blaser, eds. Campylobacter. 3rd ed. Washington: ASM, 2008. Print.

van Hees, B. C., et al. “Regional and Seasonal Differences in Incidence and Antibiotic Resistance of Campylobacter from a Nationwide Surveillance Study in the Netherlands: An Overview of 2000–2004.” Clinical Microbiology and Infection 13.3 (2007): 305–10. Academic Search Complete. Web. 29 Dec. 2015.