Vibrio parahaemolyticus is a bacterial species that contains many individual strains. The bacteria prefer to live in seawater and can be transmitted to the human intestine, especially when inadequately cooked fish and seafood are eaten. Not all strains of the bacterium are considered human pathogenic.
What is Vibrio parahaemolyticus?
In the bacterial division of Proteobacteria, the Gammaproteobacteria form a class of their own. It encompasses orders such as Vibrionales, which in turn includes the bacterial family Vibrionaceae. This family contains the genus Vibriones, which encompasses various species of Gram-negative, facultative anaerobic, and bent rod bacteria with unipolar flagella. Bacteria from this genus are capable of active locomotion thanks to their flagella. One species of vibrios is Vibrio parahaemolyticus with its individual strains. The pathogenicity of the bacteria was recorded by Fujino Tsunesaburō after a bacterial-related disease wave in Japan in 1951. Since the late 1990s, infections with Vibrio parahaemolyticus have also been common in North and South America. Cases with infections of the digestive tract have now also been documented in Europe. An enormous variety of different strains are associated with Vibrio parahaemolyticus, which are subdivided into serotypes depending on intracellular antigens. 76 serotypes have been identified to date. Twelve of them are pathogenic. The pathogenicity of other strains is still unclear so far and thus currently still corresponds to a research topic.
Occurrence, distribution, and characteristics
Facultative anaerobic bacteria grow optimally in the presence of oxygen but can also live in the absence of O2 by switching their metabolism. Thus, as a facultatively anaerobic bacterial species, Vibrio parahaemolyticus does not necessarily rely on an oxygen-rich environment to grow, although its growth is favored by oxygen. The strains of the species possess the enzymes catalase and oxidase. The ideal temperatures for growth are between 10 and – 15 degrees Celsius. The bacteria can also live well with higher temperatures, such as Celsius degrees between 20 and 30, making it a mesophilic bacterium. Like other representatives of the superordinate genus, the species Vibrio parahaemolyticus operates chemoorganotrophic as well as heterotrophic metabolism. Accordingly, the bacteria use organic compounds as a source of energy and also build cellular substances from them. The bacteria are capable of utilizing various substrates in the form of fermentation. For example, they metabolize carbohydrates such as glucose, arabinose or mannose fermentatively to form acids or similar products. Thanks to the enzymes ornithine decarboxylase and lysine decarboxylase, they are able to split carbon dioxide from amino acids such as ornithine and lysine. The natural habitat of the Vibrio parahaemolyticus species is water, where it is increasingly detected, especially in the summer months. The bacterium prefers to live in seawater, especially in brackish and coastal waters. From temperatures of about 14 degrees Celsius, the bacteria are released from the sediment and attach themselves to plankton components, resulting in transmission to fish and crustaceans. Transmission to humans can occur through the consumption of contaminated marine life such as oysters, as these are often eaten raw. Infection can also occur through inadequately treated drinking water. In individual cases, bacteria have also been observed to enter the body via minor wounds where the affected person has been swimming in contaminated water. Not all strains of the bacterium are human pathogenic. Some behave as commensals after invasion of the human organism and neither cause harm nor confer benefit.
Diseases and ailments
12 pathogenic serotypes of Vibrio parahaemolyticus have been described to date. These serotypes are primarily associated with the bacterial infection of gastroenteritis. O3:K6 is the most commonly identified serotype. This is the strain Vibrio parahaemolyticus RIMD 2210633. In addition, serotypes O1:K25, O1:K41, O1:K56, O3:K75, O4:K8, and O5:KUT are considered pathogenic. Infections with Vibrio parahaemolyticus are particularly widespread in the Asian region, for example in Japan, Taiwan or Southeast Asia.In 1998, there was an epidemic in Texas and twelve other US states. A short time later, epidemic infections were also documented in Chile. Within Europe, France was hit by the most severe cases of infection. The preferred route of infection of the Vibrio parahaemolyticus bacterial species is the fecal-oral route. Raw or insufficiently cooked fish such as mackerel, tuna, sardine and eel or seafood such as crab, squid, shrimp, lobster and mussels are considered the most common sources of infection. Less commonly, individuals acquire the infection through a wound while swimming in warm ocean water. Infection with pathogenic strains of the bacterial species causes acute gastroenteritis. Superficial wound infections and sepsis (blood poisoning) are also conceivable but rather rare symptoms. After up to one day of incubation, affected individuals experience watery diarrhea, abdominal pain, nausea, fever, and vomiting. Symptoms usually last for three days, or up to ten days in immunocompromised patients. Drug therapy is only required if the bacteria enter the bloodstream and there is a risk of sepsis. In severe cases of infection, in addition to electrolyte and fluid replacement by infusion, administration of an antibiotic such as doxycycline or ciprofloxacin takes place. Because immunocompromised patients are generally at higher risk for complications, they are generally given medications when they have an infection.
