Vibrio Vulnificus: The Deadly Pathogen

Highlights

  • Vibrio Vulnificus is a Gram negative, rod shaped pathogen
  • Vibrio Vulnificus infections can be fatal as it may cause severe wound infections 
  • It is a deadly, opportunistic human pathogen responsible for the majority of seafood-associated deaths globally

Bacteria are single-celled, microscopic organisms existing in the environment. Many types of bacteria serve a useful purpose but harmful bacteria also exist. They support forms of life like animals and plants and also used for medicinal and industrial processes. Bacteria are the first organisms on earth which appeared about 4 billion years ago.  Fossils are of bacteria-like organisms have found during excavation are the oldest. Bacteria can survive extreme conditions and use inorganic and organic food compounds. A growing interest in the gut microbiome research is providing new insights on the bacteria function in terms of human health.

Bacteria exist in radioactive waste plants, animals, soil, water, arctic ice and glaciers, deep in the earth’s crust and hot springs. Bacteria also exist in the atmosphere, stratosphere and the depth of the ocean down to 10,000 meters deep.

Types of Bacteria

Rod-shaped bacteria are called bacilli (singular bacillus). Some might also be curved known as vibrio. Spherical bacteria look like a ball such as the streptococcus group, a cause for step throat. Spiral bacteria are called spirilla (singular spirillus). The ones with a tight coil are known as spirochetes.

Structure of bacteria

Cell wall is a layer of peptidoglycan which gives the bacteria its shape. It exists outside the plasma membrane. Capsule is a layer around the cell wall in some types of bacteria. Plasma membrane generates energy and transports chemicals within the cell wall. Flagellum is used for movement of some of bacteria. Ribosomes are where proteins are synthesized. Cytoplasm is a gelatinous substance in the plasma membrane containing ribosomes and genetic material. DNA comprises of all the genetic instructions for developing the bacterium function. Pili,  hair-like appendages present around the cell so it  can stick to surfaces transferring genetic material to other cells, which is a major cause for illness in humans.

Hazards and Resistance

There are various types of harmful disease causing bacteria like bubonic plague, pneumonia, cholera, typhoid, tuberculosis and many others which can prove to be fatal for humans. Cure in the form of vaccines and antibiotics does exist. The human body, when exposed to bacteria which is not helpful will be attacked by the immune system leading to inflammation and swelling. Some bacteria develop a resistance towards antibiotic medication and medical treatment over a period of time.

Vibrio Vulnificus

Vibrio vulnificus is a rod shaped pathogen of the ‘Vibrionaceae’ family. It is a dangerous bacteria responsible for seafood-associated deaths worldwide. Infection caused by this virus can be fatal as the wounds could result in amputation or lead to sepsis in affected individuals. The treatment for this bacteria is not easy as it has started developing resistance against antibiotic treatment due to the indiscriminate use of medicines. Analyzing the antibiotic resistance of this bacteria is most vital to select precise treatment and initiate proper prevention measures to curb the further spread of infections, as it will help reduce the rate of mortality related to this pathogen globally.

This bacteria has gradually evolved to finally become resistant to drug treatments. According to the World Health Organization (WHO) the drug resistant bacteria has been declared as an international health crisis. Antimicrobial resistance is a serious threat to the human race. Unmethodical use of antibiotics in agriculture, aquaculture as well as the clinical field gave rise to the issue of antibiotic resistance. It is not a new concept, but the number of resistant pathogens are rising geographically and the level of resistance is also rising. Pathogens seem to have evolved through mutation developing a higher resistance to medicines.

Bacterial infection is the most dreadful threat to mankind. Vibrio family comprises of Vibrio parahemolyticus, Vibrio cholera and Vibrio vulnificus which are the general causes of food based infections. Such infections can be seen in humans due to contaminated seafood consumption. Apart from these infections, aquatic livestock is also affected resulting in big losses for the fishing industry. This unmethodical use of antibiotics has caused multidrug resistance in Vibrio species.

Characteristics of Vibrio vulnificus (Vv)

Vv is a member of the ‘Vibrionaceae’ family. It is found in warm weather coastal parts where the temperature of water is in the range of 9° to 31°C. The preferred habitat of the bacteria is ideally a water temperature more than 18°C having salinities between 15 and 25 parts per thousand. That is the reason, most cases of Vibrio vulnificus occur in tropical or subtropical regions. It is classified under three types based on biochemical characteristics. Biotype 1 causes severe human infection and is found globally in brackish or salt water. The entire disease spectrum is caused due to this sub type. Primary sepsis combined with the biotype rate exceeds the 50% death rate. Biotype 2, primarily eel pathogens are found in Eastern and Western Europe salt water bodies. Biotype 2 strains can cause human infections rarely. Comparison of the overall similarities revealed that the third biotype was a hybrid of biotypes 1 and 2. Biotype 3 is found in freshwater fish. It is found in Israel. Biotype 3 can cause severe human infections resulting in amputation. Death rate due to this biotype is around 8%.

Geographical occurrence of Vibrio vulnificus

Cases of Vv infections have been found in diverse climate conditions all over the world. Infections have been found in Sweden, Germany, Denmark, Turkey, Belgium, Spain, Holland, Italy, Israel, India, Japan, Taiwan, Korea, Thailand, Australia, and Brazil. Vibrio vulnificus bacteria is found in samples of seafood with studies reporting 2.4% of shrimp from Southeast Asia,  3.5–8% of seafood samples in Europe,  75% of fresh harvest of oysters in India and 100% of oysters from the Mexico Gulf during May to October.

A Burden on Healthcare

Bacterial infections have always been a strain on the aspect of the healthcare sector. The yearly health costs of seafood-related diseases in the US were found to be 350 million dollars with straight exposure to V. vulnificus, Vibrio parahaemolyticus, Vibrio alginolyticus, and aerosolized Karenia brevis amounting to over 30 million dollars. Studies have shown that premature deaths for a large population with context to the total cost of seafood illness treatment which is 306 million dollars, followed by medical care 25 million dollars, hospitalization 6 million dollars, and loss of productivity 15 million dollars, all of these combined together create a huge healthcare burden to the U.S.

  1. Vibrio vulnificus has come forth as the costliest water body based pathogen in the study with an yearly cost of illness 10 times more compared to other bacterium amounting to 66% of seafood-related diseases health costs and 26% of the total costs for health. Even more worryingly, V. ulnificusaccounts for 1/3 of the total seafood-related illness and more than 85% of the costs of direct exposure to Vibrio pathogen. These were due primarily to a high rate of premature death with a mortality rate of 31% for seafood-related infection and 18% for infections from direct exposure. This should garner the significant attention as premature death costs US$ 238 million, which accounts for 99% of the total V. vulnificus health costs and 75% of the total cost of premature deaths.
  2. Vibrio vulnificus bacteria are usually susceptible to most antibiotics of veterinary and human significance. However, the extensive use of antibiotics in health care, agriculture, and aquaculture systems has led to the increase in antibiotic resistance in many bacterial genera including Vibriospecies over the past few decade. V. vulnificus in seafood and aquatic environments are exhibiting resistance to multiple antibiotics due to the misuse of antibiotics. As multiple-antibiotic resistant bacteria pose a threat in both to fish and shellfish farming and human health, appropriate actions need to be taken as it raises serious public health and economic concerns. V. vulnificus resistance toward common antibiotics has reached alarming levels in many countries which has serious implications on the treatment methods for bacterial infections.

 

Clinical Manifestation

vulnificuscan cause serious and fatal infections in susceptible patients. This pathogen is transmitted through seafood consumption of contaminated seafood, especially undercooked or raw oysters or through direct contact or infection into open wounds. Gastroenteritis is a result of consumption of contaminated seafood (raw oysters) and the patient may vomit, feel nausea and abdominal pain which converts into chills, fevers and cutaneous manifestations. As these cases do not result in localized cellulitis or systemic shock, majority of cases go unreported.

In certain cases, V. vulnificus infection can be deadly, when it results in primary sepsis and necrotizing fasciitis. Sepsis is the most common or in some cases a close second phase of infection, and has the worst mortality rate of 50% and above. The point of entry is believed to be the small intestine. Primary septicaemia shows characteristics by bacteremia without any concentrated infection and usually comes out with sudden symptoms of fever and chills, often combined by vomiting and abdominal pain, and  extreme pain within a week after absorption of contaminated seafood, though symptom might show up in a period upto 14 days. Within the first 24 h after the symptoms of illness, secondary symptoms such as cellulitis, bullae, and ecchymoses begin to appear on patient’s health. Apart from that, septic shock, mental condition changes and thrombocytopenia were also reported in patients with primary septicaemia. Primary septicaemia can prove to be deadly in 60–75% of cases with hypotension condition in a span of 12 hours of admitting the affected person, representing a poor prognostic aspect, as these individuals have more possibility of dying in comparison to patients infected with normal blood pressure.

Treatment and Prevention

Ouick diagnosis and fast treatment with proper antibiotics is important for maximum patient recovery rate, especially in severe phases of diseases such as wound infections or systemic septicaemia. Regardless of the infection route, V. vulnificus infection does respond to antibiotic treatment as it has been clearly observed, the more delay in treatment, the higher the death rate. Several types of antimicrobials are suitable for treatment of V. vulnificus infection. Doxycycline, and ceftazidime are the best antibiotics for V. vulnificus infections in adults. The best treatment for children is trimethoprim-sulfamethoxazole (co-trimoxazole).

Conclusion

Vibrio vulnificus is a deadly bacteria and also one of the bacteria with highest treatment costs. This bacteria exists globally as it poses a serious concern for human beings. The consumption of seafood is on the rise but it comes with certain risks. One of them being Vibrio vulnificus as it affects people living in tropical, warm water bodies such as the coastal areas if they consume contaminated seafood. This bacteria can prove to be hazardous if not treated in time. Efforts are being taken by medical experts to reduce fatality rates by providing precise medical treatment.

 

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