'Campylobacter is a genus of Gram-negative, microaerophilic bacteria in the family Campylobacteraceae. Cells are generally curved, S-shaped, or spiral rods, and many species are motile by means of polar flagella. The generic name combines the Ancient Greek word kampylos, meaning curved, with the Neo-Latin word bacter, meaning rod. Members of the genus occur in humans and other animals, particularly within the gastrointestinal and reproductive tracts. Many animals carry Campylobacter without signs of disease. Human infection can result from consuming contaminated food or water or through contact with infected animals; raw or undercooked poultry is a major source. Several species cause campylobacteriosis, one of the most common bacterial causes of gastroenteritis worldwide. C. jejuni causes most reported human infections, while C. coli, C. upsaliensis, C. fetus, and C. lari are reported less frequently. Infection usually causes diarrhea, abdominal pain, and fever, but can occasionally result in bloodstream infection or post-infectious complications such as Guillain–Barré syndrome. Some species are also important veterinary pathogens. C. fetus causes bovine genital campylobacteriosis, which is associated with infertility, embryonic loss, and occasional abortion in cattle.
Morphology and phenotype Campylobacter cells are generally slender, curved, comma-shaped, S-shaped, or spiral rods. Most species are motile by one or more flagella at one or both poles, although nonmotile species occur. Members of the genus are generally microaerophilic, but oxygen requirements and optimal growth temperatures vary among species. The thermotolerant species C. jejuni grows best at 37–42 °C. Under environmental stress, including prolonged exposure to atmospheric oxygen, C. jejuni may change from a curved rod to a coccoid form. Most species are oxidase-positive, while catalase activity and nitrate reduction vary among species and have traditionally been used in phenotypic identification.
History Theodor Escherich was the first to describe in 1886 what are known today as Campylobacters in the stool samples of infants, who perished from a disease he named "cholera infantum". In the following years until the end of the century, a number of publications appeared, describing the occurrence of such "spirilla" in cases of "cholera-like" and "dysenteric" disease. These organisms were mainly found in the colon or associated with mucus in diarrhoeal stool specimens. Vibrio-like bacteria were also described by Sir John McFadyean and Stockman in 1913 in fetal tissues of aborted sheep. For several years Campylobacters were continuously referred to as Vibrio-like organisms, until 1963 when Sebald and Veron gave the name "Campylobacter" to the genus based on their shape and microaerophilic growth requirement and after showing significant biological differences with Vibrio species.
Genomics The genomes of several Campylobacter species have been sequenced, beginning with C. jejuni in 2000. These genome studies have identified molecular markers specific to members of Campylobacter. Campylobacter spp. genomes are rather small compared to those of other gastrointestinal pathogens, with sizes ranging between 1.60 and 1.90 Mbp. A characteristic of most Campylobacter genomes is the presence of hypervariable regions, which can differ greatly between different strains. Studies have investigated the genes responsible for motility in Campylobacter species. Some Campylobacter species contain two flagellin genes in tandem for motility, flaA and flaB. These genes undergo intergenic recombination, further contributing to their virulence. A single Type VI secretion system (T6SS) cluster was also predicted in approximately one-third of Campylobacter species, grouping into three distinct organisations and harbouring up to five vgrG genes.
Phylogeny Nomenclature follows the List of Prokaryotic names with Standing in Nomenclature (LPSN), with the National Center for Biotechnology Information (NCBI) taxonomy database used as an additional reference. The trees below compare a 16S rRNA gene phylogeny from LTP_all_07_2026 with the genome-based GTDB R11-RS232 reference tree. Only species with validly published and correct names in LPSN that are represented in the respective source tree are shown.
The LPSN-recognized species C. australis, C. devanensis, C. parajejuni, C. porcelli, and C. vicugnae are not represented under those names in LTP_all_07_2026. C. australis, C. felis, C. ovis, and C. parajejuni are not represented under those names in GTDB R11-RS232.
Campylobacter-specific bacteriophages Campylobacter-specific bacteriophages are natural viral predators of the organism. Bacteriophages specific to the species now known as C. coli and C. fetus (previously Vibrio coli and V. fetus), were first isolated from cattle and pigs during the 1960s, and Campylobacter bacteriophage therapy is an ongoing area of research in the age of bacterial antibiotic resistance.
Pathogenesis
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