Campylobacter

Campylobacter species are slender, curved, Gram-negative rods with a characteristic corkscrew motility driven by a single polar flagellum. They are microaerophilic, requiring reduced oxygen (3–15%) and increased carbon dioxide for growth, and are thermophilic, with optimal growth at 42°C, which aligns with the avian body temperature. The bacteria colonize the mucus layer of the intestinal tract, using chemotaxis and adhesins to attach to epithelial cells. Pathogenesis involves the production of cytolethal distending toxin (CDT), which causes host cell cycle arrest and apoptosis, and the activation of inflammatory pathways leading to diarrhea. C. jejuni also exhibits molecular mimicry between its lipooligosaccharides and gangliosides, which is linked to the autoimmune complication Guillain-Barré syndrome.

Campylobacteriosis is one of the most common bacterial gastroenteritis worldwide, with an estimated 95 million cases annually. Poultry is the primary reservoir, and handling or consuming undercooked chicken accounts for a majority of infections. Other sources include unpasteurized milk, contaminated water, and contact with infected animals, particularly puppies and kittens. The infectious dose is low, as few as 500 organisms, and person-to-person spread is rare. Outbreaks are often linked to water contamination or food processing failures. In developing countries, the disease is hyperendemic in children, often leading to asymptomatic carriage, whereas in industrialized nations it presents as acute gastroenteritis. Surveillance data from the CDC and WHO highlight its significant economic burden due to healthcare costs and lost productivity.

Clinical manifestations typically appear 2–5 days after exposure and include watery or bloody diarrhea, abdominal pain, fever, and malaise. The illness is usually self-limiting, lasting 3–7 days, but can be severe in immunocompromised individuals. Dehydration is the main concern, and oral rehydration is the primary treatment. Antibiotics such as macrolides (e.g., azithromycin) or fluoroquinolones are reserved for severe or prolonged cases, though resistance to fluoroquinolones is rising globally. Complications include bacteremia, reactive arthritis, and Guillain-Barré syndrome, which occurs in approximately 1 in 1,000 infections and is the most common cause of acute flaccid paralysis worldwide. Post-infectious irritable bowel syndrome is also increasingly recognized.

Beyond C. jejuni and C. coli, other species like C. fetus cause systemic infections in immunocompromised hosts, and C. ureolyticus is associated with periodontal disease. The genus was first isolated in 1906 from cattle, but its role in human disease was not recognized until the 1970s due to the need for selective culture media. Campylobacter species are also significant in veterinary medicine, causing avian hepatitis and reproductive disorders in livestock. A notable niche application is the use of bacteriophages to control Campylobacter in poultry, an area of active research. Additionally, the bacterium's ability to form biofilms on food processing surfaces complicates eradication. The genome of C. jejuni is small (~1.6 Mb) and highly variable, contributing to its adaptability and antigenic diversity.

Campylobacteriosis

The infectious disease caused by Campylobacter bacteria, typically resulting in gastroenteritis.

Microaerophilic

Requiring a low oxygen concentration (typically 3–15%) for growth.

Guillain-Barré syndrome

An autoimmune disorder affecting the peripheral nervous system, often triggered by Campylobacter infection.

Cytolethal distending toxin

A toxin produced by Campylobacter that causes host cell cycle arrest and apoptosis.