Let's explore the clinical presentation, method of entry, prevention strategies and research surrounding infection with Vibrio vulnificus bacteria.
Introduction
Vibrio vulnificus is a marine bacteria found globally in warm saltwater environments. Infection in humans commonly occurs via two routes, either by entering through wounds or by consumption of infected seafood. V. vulnificus infection through either route can result in incredibly life-threatening symptoms with high mortality rates.1
Where would you encounter V. vulnificus?
Vibrio vulnificus bacteria can be found in saltwater environments, or brackish waters, meaning where fresh and saltwater mix, for example where a river meets the sea. V. vulnificus can be found worldwide but is normally not found in water temperatures below 20 degrees Celsius.3 This means that populations living in coastal regions in warmer areas of the world are at higher risk of Vibrio vulnificus infection. Areas with monsoon rain patterns in subtropical climates in the Northern Hemisphere have been shown specifically to bear the large majority of infection.
Consequently, over 95% of infections occur in South Korea, Japan and the Taiwan Pacific regions, as well as the United States and Gulf of Mexico Atlantic regions.4 Warm sea surface temperatures can promote proliferation of V. vulnificus, meaning that rising sea temperatures due to global warming could contribute to rising infections over the last 20 years or more.4,6
How does V. vulnificus cause disease?
There are two main types of disease caused by a V. vulnificus infection. If ingested, often through uncooked seafood, most commonly oysters, infection causes gastrointestinal diarrhoea and vomiting symptoms and can lead to septicaemia, a dangerous bloodstream infection. If V. vulnificus enters through a wound, it can lead to necrosis, which means the infection is causing death of soft tissues around the wound, which, if left untreated, can lead to amputation, septicaemia, or even death.
What are the risk factors for getting V. vulnificus?
- Risk factors for wound infections with V. vulnificus are contact with saltwater environments with open or unhealed wounds and any activities in salt water environments where there is a risk of injury, for example, water sports and fishing
- Risk factors for gastrointestinal V. vulnificus infection are consumption of raw and uncooked seafood, specifically oysters
- People involved in preparation of seafood are also at higher risk of contracting V. vulnificus, by ingestion of bacteria or through wound entry due to contact with bacteria
What are the symptoms?
Wound infections
Wound infection with Vibrio vulnificus can be identified by the formation of skin lesions around the wound through which the bacteria has entered. Cellulitis is a common symptom of infection, characterised by swelling, redness of the skin, pain, and the skin becoming hot to the touch. This can be accompanied by lesions and bruising.
Furthermore, fluid-filled blisters may be observed at the site of infection. If untreated, this may progress to necrotising fasciitis, which means soft tissue death in the area. This can be characterised by redness, swelling, and pain, accompanied by nausea and vomiting, possibly progressing to the development of black or purple regions on the skin. In healthy patients, mortality from a V. vulnificus wound infection could be as high as 25%.7
Gastrointestinal infections
After consumption of infected seafood, early symptoms include fever, chills, clamminess, diarrhoea and vomiting. These symptoms may coincide with septicaemia or precede it. Symptoms of septicaemia include chills, rapid heart rate, low blood pressure and even confusion or delirium. The rate of mortality of this type of infection is as high as 50% once symptoms present.7
How dangerous is it?
V. vulnificus infection is a dangerous infection. Some coexisting conditions can, however, increase mortality rates considerably. Immunosuppressant medications and chronic diseases, specifically poor liver function and diabetes all increase the risk of progression to septicaemia, and therefore fatalities.6,3
Diagnosis and detection
Early diagnosis of V. vulnificus infection means treatment can be started as soon as possible, thus stopping the bacteria from multiplying and spreading throughout the body. This can improve the prognosis of the disease.3 Therefore, if there is reason to suspect the presence of a V. vulnificus infection, it is important to seek prompt medical advice, disclose all symptoms and be open about the patient's contact with risk factors, such as saltwater environments or seafood, as well as pre-existing medical conditions which may elevate the risk of severe infections.
A V. vulnificus infection is diagnosed through recognition of symptoms in combination with exposure to risk factors such as saltwater environments or seafood.
Blood tests will show clinical indications of a standard bacterial infection, but stool, blood or samples taken from wound infections can be sent to the lab and cultured. Culturing and laboratory testing can help to identify the presence of V.vulnificus.
Treatment and management
Treatment of V. vulnificus infection is primarily antibiotic therapy for both gastrointestinal and wound infections.
Combination antibiotic therapy including doxycycline is recommended as a first response.7,10 Ospitalisation is commonly recommended or required for treating V. vulnificus infection.
With wound infection, the wounds must be well managed, regularly cleaned, blisters and abscesses drained, and, in severe cases, amputation may be considered where the risk of mortality is high. Gastrointestinally-infected patients must be given fluids to prevent dehydration, and anti-emetic (anti-vomiting) drugs are recommended for the management of symptoms, alongside antipyretics; drugs for managing fevers.7
Prevention strategies
Prevention strategies include avoiding saltwater environments with wounds, new tattoos or piercings, and wearing protective equipment to prevent exposure of wounds in such environments.11
Additionally, properly cooked seafood, specifically shellfish and oysters, can kill V. vulnificus bacteria, therefore proper food hygiene and preparation are paramount. When handling or preparing raw seafood, gloves and other protective equipment should be worn, hands regularly washed, hygiene protocols observed and surfaces and equipment thoroughly cleaned.3
Public health concerns
Reporting of V. vulnificus infections is crucial, as global warming may facilitate the spreading of the bacteria to new regions previously uninhabited by the bacteria. Additionally, since awareness of risk factors and symptoms are critical to early diagnosis and consequently better disease outcomes, surveillance of the geographic distribution of cases can help to inform regional and national healthcare services and may aid in faster diagnoses.4
The Centers for Disease Control and Prevention (CDC) in the USA, one of the nations affected by V. vulnificus infections, recommend that all cases should be reported to local and state health departments so that instances can be adequately monitored.
The CDC recommendations for public health management of infections are:
- ongoing education of tourists
- at-risk populations
- food preparation staff and medical professionals on the risk factors of infection
- prevention strategies
- clinical presentations and disease management12
These recommendations aim to lower infection rates, educate the public, and aid early diagnosis and treatment by medical professionals.
Research and future direction
Antibiotic resistance is a concern for the ongoing management of V. vulnificus infections, as resistance is rising, potentially rendering future cases even more dangerous.11 Consequently, ongoing research into resistance is important to ensure appropriate antibiotics are selected when beginning treatment, as early response is vital to improve disease outcomes.11
To combat antibiotic resistance, prevention of infection is a more effective strategy against V. vulnificus. Research is currently looking into a possible vaccine to prevent infection, but this is as yet unavailable. Some recent clinical studies have shown some promise at protecting against infection, so we look hopefully towards developing a successful V. vulnificus vaccine in the near future.11
Summary
In conclusion, Vibrio vulnificus is a marine bacterium which can cause life-threatening infections with high mortality. It has two main routes of infection leading to two distinct diseases. Oral onsumption of V. vulnificus can lead to a gastrointestinal infection and ultimately septicaemia. Infection through wounds often result in cellulitis. This can progress to necrotising infection resulting in soft tissue death and potentially septicaemia.
Both of these disease presentations can be fatal, particularly in patients with an already compromised immune system. Properly preparing seafood, washing hands and wearing gloves when around seafood preparation, avoiding saltwater environments with open wounds, or taking steps to prevent injury in saltwater environments can be effective methods to minimise infection risk.
Infections should be carefully reported and tracked so that authorities can be aware of the geographic distribution of infections, and any symptoms of either disease presentation should be assessed by a medical professional as soon as possible.
References
- Jones MK, Oliver JD. Vibrio vulnificus : Disease and Pathogenesis. Infect Immun [Internet]. 2009 [cited 2024 Jan 18]; 77(5):1723–33. Available from: https://journals.asm.org/doi/10.1128/IAI.01046-08.
- Bross MH, Soch K, Morales R, Mitchell RB. Vibrio vulnificus infection: diagnosis and treatment. Am Fam Physician. 2007; 76(4):539–44.
- Huang K-C, Weng H-H, Yang T-Y, Chang T-S, Huang T-W, Lee MS. Distribution of Fatal Vibrio Vulnificus Necrotizing Skin and Soft-Tissue Infections: A Systematic Review and Meta-Analysis. Medicine (Baltimore). 2016; 95(5):e2627.
- Martinez-Urtaza J, Bowers JC, Trinanes J, DePaola A. Climate anomalies and the increasing risk of Vibrio parahaemolyticus and Vibrio vulnificus illnesses. Food Research International [Internet]. 2010 [cited 2024 Jan 18]; 43(7):1780–90. Available from: https://www.sciencedirect.com/science/article/pii/S0963996910000980.
- Haftel A, Sharman T. Vibrio vulnificus Infection. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2024 Jan 18]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK554404/.
- Heng S-P, Letchumanan V, Deng C-Y, Ab Mutalib N-S, Khan TM, Chuah L-H, et al. Vibrio vulnificus: An Environmental and Clinical Burden. Frontiers in Microbiology [Internet]. 2017 [cited 2024 Jan 18]; 8. Available from: https://www.frontiersin.org/articles/10.3389/fmicb.2017.00997.
- Health Alert Network (HAN) - 00497 | Severe Vibrio vulnificus Infections in the United States Associated with Warming Coastal Waters [Internet]. 2023 [cited 2024 Jan 18]. Available from: https://emergency.cdc.gov/han/2023/han00497.asp.