Campylobacter is the name given to a bacterial genus belonging to the division Proteobacteria and family Campylobacteraceae. The genus contains pathogenic bacteria in addition to species that inhabit the intestine as commensals. Campylobacter jejuni and Campylobacter coli are considered the causative agents of Campylobacter enteritis.
What are campylobacters?
Within the bacterial division Proteobacteria and the class Epsilonproteobacteria, the family Campylobacteraceae is listed under the order Campylobacterales. Campylobacter forms one bacterial genus of this family. The genus name is derived from the Greek, where the name literally means “crooked staff”. Thus, the species from the genus Campylobacter are rod-shaped bacteria with a corkscrew shape, also known as spirillae. The genus shows gram-negative staining behavior, is microaerophilic as well as polar flagellated. In 1963 the bacterial genus was described by Sebald and Veron. Until then, individual species of Campylobacter were referred to as microaerophilic vibrios. It was not until the 1960s that they were no longer classified in the family Vibrionaceae. The cell size of the bacteria ranges from 0.2 to 0.8 on 0.5 and five micrometers. They often bear a single flagellum at one end. However, some members of the genus are also bipolarly flagellated and thus carry flagella at both ends. This allows them to actively move around. In culture, some of the bacteria of the genus change from corkscrew-shaped to coccus-shaped. Many species of Campylobacter possess catalase and oxidase. Those of the species Campylobacter sputorum, concisus, mucosalis, and helveticus do not possess catalase. Medically, the species Campylobacter fetus subsp. fetus, coli, jejun subsp. jejuni have the highest relevance.
Occurrence, distribution, and characteristics
Organotrophy refers to the demand for reducing agents from organic matter that provides energy-supplying redox reactions in the energy metabolism of chemotrophic organisms. In chemotrophy, the energy demand of an organotrophic living organism is met by exergonic metabolic conversions. The species of the bacterial genus Campylobacter are all chemoorganotrophs. They are so-called nitrate breathers. Accordingly, they operate an oxidative energy metabolism by utilizing nitrate as an oxidant. In aerobic respiration, oxygen is used instead of nitrate. By utilizing nitrate, the Campylobacter genus is not dependent on O2. Amino acids and individual intermediates of the tricarboxylic acid cycle, which can be oxidized by nitrate, are used as electron donors. Just as little as oxygen, the genus Campylobacter does not use carbohydrates for its metabolism. For this reason, the individual species of the genus are considered microaerophilic. In other words, they are aerobic microorganisms that grow ideally in a low oxygen concentration in the growth environment. Oxygen concentrations of less than 20 percent are considered optimal. Species such as Campylobacter jejuni live in drinking water or food, among other places. Most species tolerate low temperatures but die at higher temperatures. For this reason, cooking meat through can kill them, for example. An ideal environment for the species is the intestine of living organisms. Some species of Campylobacter occur as commensals in the intestines of cats, dogs, cattle and also humans. These species do not cause disease. They do not harm the host any more than they benefit it. Other species of the genus are pathogenic and thus may be the causative agent of various diseases. Zoonosis is present in the genus. This means that the bacteria can be transmitted from humans to animals and in the opposite direction. For this reason, close contact with contaminated animals is a possible source of infection. In addition, the pathogens are often present in animal foods, especially raw cow’s milk, raw meat, and raw nuts. From person to person, the bacteria of the Campylobacter genus are usually transmitted in the form of smear infection. This means that the bacteria can be transmitted just by touching a contaminated person.
Diseases and symptoms
Campylobacter jejuni and Campylobacter coli are among the best known and most important pathogens of the Campylobacter genus. Both bacterial species are associated primarily with diarrheal disease.For example, they can cause Campylobacter enteritis, which corresponds to bacterial gastroenteritis. After salmonella gastroenteritis, this form of enteritis is the second most common form of infectious diarrheal disease in Germany. The peak period of occurrence is summer. Since bacteria of the genus Campylobacter are widespread in animals, infection usually occurs through contact with contaminated animal-based foods. The most common causes of infection are consumption of raw milk and contaminated poultry. The incubation period of infection is up to five days. After that, relatively unspecific symptoms develop, which are mainly characterized by headache and pain in the limbs as well as fever and exhaustion. These initial symptoms are followed by a severe form of diarrhea. This is often bloody diarrhea, which may be associated with colic-like pain. The diarrhea may last up to ten days. A small proportion of affected patients develop reactive arthritis weeks later, which manifests as arthralgias (joint pain). Campylobacter enteritis has also been discussed as a possible trigger for Guillain-Barré syndrome disease in some rare cases. This is a polyneuritis of the peripheral nerves and spinal nerve roots. The cause of its occurrence has not yet been conclusively determined. A connection with Campylobacter is conceivable. However, the apparently related occurrence of enteritis and the syndrome does not necessarily describe a causal relationship but may be due to the general debilitation of patients after enteritis.
