What is Vibrio diseases ?
Vibrios are gram-negative, curved, rod-shaped bacteria that are natural inhabitants of the marine environment and estuarine waters. Due to their flexible physiology, vibrios can persist in a variety of aquatic ecosystems where they interact with different biotic and abiotic surfaces. In particular, it has been demonstrated that plankton organisms, mainly copepods, host a large population of bacteria and seem to represent a plausible aquatic reservoir of V. cholerae and other vibrios.
Pathogenic vibrios cause 3 major syndromes of clinical illness : gastroenteritis, wound infections, and septicemia. The most common clinical presentation of Vibrio infection is self-limited gastroenteritis ; many cases of Vibrio-associated gastroenteritis are substantially underrecognized because vibrios are not readily identified in routine stool cultures.
Epidemiologic data suggest that the majority of vibrios infections are foodborne and associated with consumption of raw or undercooked shellfish. Other infections derived from exposure of wounds to warm seawater. Patients with liver disease are at particularly high risk for significant morbidity and mortality associated with these infections.
The Vibrio species of most medical significance include Vibrio cholerae, Vibrio vulnificus, and Vibrio parahaemolyticus although there are at least 12 pathogenic Vibrio species recognized to cause human illness. Early detection and initiation of treatment of these infections are very important, particularly for cholera and invasive Vibrio infections, because these may rapidly progress to death. There is an increasing evidence supporting the role of halophylic vibrios as both human pathogens and a reservoir of Vibrio virulence genes.
Vibrio cholerae is often found in the aquatic environment and is part of the normal flora of brackish water and estuaries. It is often associated with algal blooms (plankton) which are influenced by the temperature of the water. Human beings are also one of the reservoirs of the pathogenic form of Vibrio cholerae. More recently, other substrates sustaining adhesion of vibrios have been identified such as marine plants and chironomid eggs. It is important to distinguish the toxin-producing V. cholerae O1 and O139 from the non-toxin-producing V. cholerae. The former give rise to cholera disease, which is mainly known from developing countries, whereas the latter may be found in seawater and can lead to infection, e.g. with the skin as the portal of entry.
Other pathogenic vibrios species.
Vibrio vulnificus is a bacterium in the same family as those that cause cholera. It normally lives in warm seawater and is part of a group of vibrios that are called "halophilic" because they require salt to grow. V. vulnificus can cause disease in those who eat contaminated seafood or have an open wound that is exposed to seawater. Among healthy people, ingestion of V. vulnificus can cause vomiting, diarrhea, and abdominal pain. In immunocompromised persons, particularly those with chronic liver disease, V. vulnificus can infect the bloodstream, causing a severe and life-threatening illness characterized by fever and chills, decreased blood pressure (septic shock), and blistering skin lesions. V. vulnificus bloodstream infections are fatal about 50% of the time.
V. vulnificus can also cause an infection of the skin when open wounds are exposed to warm seawater ; these infections may lead to skin breakdown and ulceration. Persons who are immunocompromised are at higher risk for invasion of the organism into the bloodstream and potentially fatal complications. Infections are seasonal : over 85% occur between May and October.
Vibrio parahaemolyticus lives in brackish saltwater and causes gastrointestinal illness in humans. V. parahaemolyticus naturally inhabits coastal waters and is present in higher concentrations during summer ; it is a halophilic, or salt-requiring organism. When ingested, V. parahaemolyticus causes watery diarrhea often with abdominal cramping, nausea, vomiting fever and chills. Usually these symptoms occur within 24 hours of ingestion. Illness is usually self-limited and lasts 3 days. Severe disease is rare and occurs more commonly in persons with weakened immune systems. Most people become infected by eating raw or undercooked shellfish, particularly oysters. V. parahaemolyticus can also cause an infection of the skin when an open wound is exposed to warm seawater.