Campylobacter
Campylobacter is a slender, curved-rod, gram-negative bacterium and a leading cause of bacterial gastroenteritis globally. The primary species responsible for human infections is Campylobacter jejuni, which accounts for around 90% of cases. It thrives in nonacidic environments and can be found in unchlorinated water, as well as in the intestines of birds and other animals, particularly poultry. Human infections primarily occur through the consumption of contaminated food, water, or unpasteurized milk, as well as through direct contact with fecal material. Symptoms of infection, known as campylobacteriosis, typically include diarrhea and can range in severity, with some individuals developing complications like Guillain-Barré syndrome.
The incidence of Campylobacter infections is notably higher in rural areas, possibly due to greater consumption of raw milk. Although many people recover without severe consequences, there is growing concern over the bacteria's increasing resistance to antibiotics, particularly fluoroquinolones. As a response to the public health impact of Campylobacter, some countries have initiated campaigns aimed at reducing its prevalence in the food supply, particularly within poultry production. Understanding the transmission routes and risk factors associated with Campylobacter can help in developing strategies to minimize infections.
Campylobacter
- TRANSMISSION ROUTE: Direct contact, ingestion
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 of 3 to 5 percent oxygen and 2 to 10 percent carbon dioxide. It is sometimes found in unchlorinated 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 government of New Zealand instituted a public health campaign, the Campylobacter Action Plan, in the early 2020s to help combat this issue. The campaign mainly focused on steps to reduce the levels of Campylobacter through the poultry food chain. By 2024, the rate of New Zealand-acquired foodborne illness caused by the bacteria Campylobacter had fallen to 77 cases per 100,000 population.
Humans are infected by consuming 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 1.5 million people experience symptomatic Campylobacter infections each year in the United States. The incidence of such infections is 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 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 due to the bacterial presence, or it may result from toxins 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 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 acquired immunodeficiency syndrome (AIDS) have a greater incidence of Campylobacter than those without AIDS. Some persons without AIDS have an immune deficiency in immunoglobulin A (IgA), thus increasing their risk for infection with Campylobacter. Breastfed 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
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 prevent disease. As a result, erythromycin (for children) and tetracycline (for adults) became 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, however, have become first-line treatments.
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
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