General Characteristics and Morphology
The genus name derives from the Greek campylos, meaning 'bent' or 'curved'. Approximately 18 species of campylobacters are currently described, with C. jejuni (the main pathogen), C. fetus, and C. coli holding the greatest clinical significance.
morphologically, these are small Gram-negative microorganisms: 0.5–5 µm in length and 0.2–0.5 µm in width. Cells feature a characteristic spiral shape resembling a comma or the Latin letter S. In smears, they often appear in pairs, creating clusters that resemble 'flying gull wings'.
Campylobacters are motile via a single polar flagellum (monotrichous). They do not form spores or capsules. A hallmark feature is marked polymorphism: as the bacterial culture ages, spiral forms transform into coccoid forms.
Cultural and Biochemical Properties
These microorganisms are microaerophiles and capnophiles. Successful growth requires a specific gas atmosphere with reduced oxygen concentration and elevated carbon dioxide. The optimal pH is 7.0, while temperature preferences vary by species (most commonly 37 °C or 42 °C, less frequently 25 °C).
Campylobacters are fastidious. They are cultured on complex media enriched with blood, hemin, amino acids, and protein hydrolysates. Antibiotics are routinely added to suppress accompanying flora and ensure medium selectivity.
- Metabolism: strictly respiratory. These bacteria are incapable of fermenting carbohydrates.
- Energy sources: organic acids, including amino acids.
- Enzymatic activity: weak. Microorganisms are oxidase- and catalase-positive, reduce nitrates, and produce hydrogen sulfide ($H_2S$).
Note on terminology: While traditionally grouped with Helicobacter and Arcobacter in the family Campylobacteraceae, they share distinct metabolic features.
Pathogenicity Factors and Antigenic Structure
Bacteria possess somatic (O) and flagellar (H) antigens, based on whose combinations about 60 serovars are recognized. Plasmids present within the cells determine resistance to antimicrobial drugs.
Pathogenic potential is driven by the following factors:
- Endotoxin — a structural component of the cell wall (lipopolysaccharide) released upon bacterial lysis.
- Exotoxins (produced by select strains): a cholera-like enterotoxin that triggers profuse diarrhea, and a cytotoxin that directly damages host cells.
In the external environment, campylobacters have low persistence. They are rapidly inactivated by heat, routine disinfectants, and other physical and chemical stressors.
Epidemiology and Clinical Manifestations
Campylobacteriosis is a zoonosis with a worldwide distribution. Human susceptibility is extremely high. While cases occur year-round, a summer-autumn epidemiological peak is typical.
- Reservoir and source: primarily agricultural livestock and poultry. Infected humans rarely serve as sources of transmission.
- Transmission routes: alimentary (foodborne), waterborne, contact-with-animals, and sexual.
Pathologies associated with Campylobacter are divided into four groups:
- Gastrointestinal tract involvement (enterocolitis, diarrhea) with potential systemic spread leading to sepsis.
- Localized extraintestinal manifestations (endocarditis, CNS involvement such as encephalitis and meningitis).
- Purulent-inflammatory conditions in newborns.
- Oral cavity pathologies.
Classic gastroenteritis develops after an incubation period of 2–3 days. The disease presents acutely with intoxication symptoms, fever, vomiting, and diarrhea. The clinical picture typically resolves within 10 days.
Diagnosis, Treatment, and Prevention
The primary diagnostic method is bacteriological culture. Samples include stool, vomitus, or gastric lavage fluid. Inoculation is performed on blood or erythritol agar supplemented with iron-sulfite-pyruvate components. Species differentiation relies on the ability of strains to grow at various temperatures.
Bacterioscopy of fecal smears can reveal microorganisms with characteristic morphology ('flying gull/swallow wings'). Serological tests (complement fixation, indirect hemagglutination, agglutination) and rapid diagnostics using direct immunofluorescence (DFA) with labeled sera are also utilized. K Etiotropic treatment involves antibiotics, with erythromycin and ciprofloxacin as drugs of choice. Specific prophylaxis (vaccination) is not available; control relies on sanitary and anti-epidemic measures analogous to salmonellosis prevention.