Campylobacter jejuni

Campylobacter jejuni is a curved, comma-shaped, rod-shaped, non-spore-forming, Gram-negative, microaerophilic bacterium that exhibits lively motility due to flagella at one or both ends of its cell body. It also possesses a capsule but does not form spores. As a microaerophile, it cannot grow under normal atmospheric conditions or in an oxygen-free environment.

Campylobacter jejuni is widely found in the bodies of animals such as birds, poultry, dogs, and cats. It can cause infections through contamination of meat, milk, and water that hasn’t undergone proper sanitation. Foods implicated include raw or undercooked chicken, as well as improperly pasteurized milk, egg products, and raw ham, among others.

For decades, Campylobacter has been recognized as both a pathogenic and commensal bacterium in livestock. Specifically, Campylobacter jejuni and Campylobacter coli have been isolated from a wide range of laboratory animals, including dogs, cats, guinea pigs, hamsters, ferrets, non-human primates, poultry, rabbits, as well as healthy pigs, sheep, and cattle. Campylobacter jejuni is a zoonotic pathogen capable of causing diverse diseases in both humans and animals, and it also ranks as a major foodborne pathogen—largely responsible for bacterial diarrhea worldwide. Most reports on the transmission of Campylobacter jejuni between pets and humans highlight that diarrheic puppies or kittens acquired from animal farms often serve as the primary source of infection. Consequently, individuals living with dogs are at an increased risk of contracting Campylobacter. The bacterium’s virulence factors encompass four key mechanisms: adhesion, invasion, toxin production, and molecular mimicry. Notably, the molecular mimicry pathway can trigger one of the most severe complications—Guillain-Barré syndrome.

Campylobacter jejuni is a foodborne pathogen primarily transmitted through contaminated food and water, but it can also spread via direct contact with insects, animals, and other sources.

Campylobacter jejuni shares O, H, and K antigens in its antigenic structure with enteric bacteria. Campylobacter jejuni is a common commensal bacterium found in various animals, including cattle, sheep, dogs, and poultry. These animals harbor high levels of the bacteria in their reproductive tracts or intestines, making it possible for food and water to become contaminated through childbirth or excretions.

The population is generally susceptible, with the highest incidence among children under 5 years old, and cases are most common during summer and autumn. Flies also play a significant role as vectors. Infection can also occur through direct contact. Infected mothers may transmit the virus to their unborn babies during delivery.

Clinical manifestations of Campylobacter jejuni infection include fever, diarrhea, vomiting, and muscle pain, leading to tissue damage in the jejunum, ileum, and colon, and enabling the bacteria to invade the bloodstream via the intestinal mucosa.

Campylobacter jejuni typically causes abortion in livestock, and these bacteria can be shed over time in the feces of asymptomatic carriers. Moreover, multiple strains of Campylobacter and Helicobacter pylori can be isolated from the feces of individual animals or even a single host.

Campylobacter jejuni produces endotoxins that can invade the mucous membranes of the small and large intestines, leading to acute gastroenteritis. It can also trigger outbreaks or epidemics of diarrhea. The typical incubation period is 3 to 5 days, and the bacteria primarily target the jejunum, ileum, and colon in humans. Main symptoms include diarrhea and abdominal pain, sometimes accompanied by fever, and occasionally vomiting and dehydration. In rare cases, the bacteria may penetrate the bloodstream through the intestinal lining, causing sepsis and infections in other organs, such as meningitis, arthritis, and pyelonephritis. Notably, there have been reports of the youngest patient to date diagnosed with pericardial myocarditis linked to Campylobacter jejuni infection.

Pregnant women infected with this bacterium may experience miscarriage, premature birth, and can even lead to neonatal infection. After infection, specific serum antibodies are produced, which help enhance the function of phagocytic cells. Currently, intestinal-specific secretory IgA antibodies have not yet been detected.

Campylobacter jejuni is not highly resistant and can be easily killed by drying, direct sunlight, and even mild disinfectants—specifically, it’s inactivated at 56°C within 5 minutes. It remains sensitive to antibiotics such as erythromycin, neomycin, gentamicin, tetracycline, chloramphenicol, and kanamycin. However, in recent years, numerous drug-resistant strains—and even multidrug-resistant ones—have been identified. Despite this, Campylobacter jejuni generally retains sensitivity to several antibiotics, with erythromycin and tetracycline commonly used for treatment.

References

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[7] Shang Xiaochun, Zhou Xiaohong, Shuai Huiqun, Huang Qinghong, Zhao Xueqin, Xu Haoyue. Epidemiological and Pathogenic Study of an Outbreak of Campylobacter jejuni-Related Foodborne Illness [J]. Chinese Journal of School Health, 2020, 41(11):1741-1744.