Commas, or carnivorous bacteria in the waters of the Baltic Sea. Next to cyanobacteria, another threat to bathers

Proven content

It is not the first time when the holiday season is in full swing in the media about the tragic consequences of bathing in the Baltic Sea. The cause, however, is not cyanobacteria, but bacteria – Vibrio commas. This year, the topic was publicized by the German station “Deutsche Welle”, but the commas are not only found in the coastal waters of Germany. They have already been observed in previous years in Denmark, Sweden and Poland. These bacteria cause, among others, Wound infections that are dangerous to health, and even sepsis.

Vibriosis – from cholera to sepsis

Last year, an infection with commas while swimming in the sea resulted in the death of an elderly woman in northeastern Germany. The authorities of the federal state of Mecklenburg-Pomerania said that the bacteria infected four more people there. All victims were at risk, i.e. they were elderly and / or diabetic, and had problems with the liver or immune system. In 2019, as many as 11 infections with Vibrio strains were recorded in Germany, but taking into account the lack of registration obligation, there could be many more of them.

We know of 36 species of commas, but only 12 of them can cause human infections. First of all, it is worth mentioning: Vibrio cholerae, V. vulnificus and V. parahaemolyticus.

Infection caused by V. cholerae is an acute, infectious disease of the digestive tract known to us – cholera. The infection occurs through the consumption of contaminated water, food or direct contact with the sick person. Cholera is found mainly in countries of the equatorial and subtropical zone. In Poland, it is extremely rare, it is usually imported from Asia (India, Bangladesh, Yemen), Africa and South America.

While cholera is responsible for outbreaks, the rest of these bacteria cause gastroenteritis, wound infections, ear infections, and occasional sepsis. These infections are called vibriosis. V. parahaemolyticus is the most common cause of gastroenteritis resulting from the consumption of contaminated seafood. In contrast to V. vulnificus, the mortality rate from primary sepsis or severe wound infections due to it is over 50%.

Commas multiply in the waters of the Baltic Sea in hot weather

Vibrio commas are ubiquitous in warm estuary waters (where rivers emerge into the seas) and coastal waters with low to moderate salinity. However, we have been observing them for some time not only in tropical or subtropical waters. The bacteria V. vulnificus and V. parahaemolyticus are found in the salty and mixed coastal waters of the Baltic Sea and the Vistula Lagoon. Wherever the water temperature exceeds 16 ° C.

According to data collected by bacteriologist Dr. Craig Baker-Austin from the British Center for Environment, Fisheries and Aquaculture Science (Cefas), conducting research on commas in the Baltic Sea, the most favorable conditions for the growth of bacteria occur when the temperature on the water surface exceeds 18 degrees C, i.e. in the months from June to September.

During the heat wave that hit Europe in 2006, when extremely high temperatures lasted over a month – from June 26 to July 30, 2006, numerous clusters of bacteria of the genus Vibrio were observed in the Baltic Sea. There have also been many reports of wound infections attributed to sea bathing. Unfortunately, there is no obligation to keep vibration disease statistics in Europe. Thus, the highest number of cases in Finland and Sweden (125 and 68 respectively) is rather a reflection of the diligence of their recording.

Dr. Baker-Austin also records many deaths (eg in Sweden, Germany and Poland in 2006, in Germany in 2003 and 2010); mainly caused by V. vulnificus (10) and V. cholerae (4). The vast majority of infections occurred during the summer (90%), and especially intensified in the hottest years: 2003 (19 cases), 2006 (66 cases) and 2010 (35 cases).

Scientists emphasize that the aging society is more at risk of vibriosis, because the number of people at risk is also growing. The UN predicts that in 2050 as much as 33 percent. of the population will be over the age of 65, so more of these people will be living and relaxing by the sea. Currently, more than 5 million citizens of the countries bordering the Baltic Sea live within 30 km from the coast.

How does infection with Vibrio bacteria occur?

Bacteria penetrate our body through open wounds during sea baths. The conjunctiva and the ears are also at risk of infection.

They are commonly referred to as carnivorous bacteria – why? Prof. dr hab. Waleria Hryniewicz, a specialist in the field of medical microbiology, explains: – This means that they destroy tissues, including muscles, causing necrotic and disintegrating changes. Most often these are necrotic changes in the fascia, but also in the muscles

You can get infected by eating raw or undercooked shellfish, especially oysters, or by swallowing contaminated water.

The elderly, chronically ill, treated with immunosuppressants, but also newborns, infants and young children are at risk.

Symptoms of infection include watery diarrhea, abdominal pain, nausea, vomiting, fever, and chills. They usually occur within a day after eating contaminated food and last an average of three days. It is advisable to irrigate and replenish electrolytes.

Other symptoms depend on where the bacteria entered, and include wound infection, otitis media, otitis externa, and conjunctivitis. Most cases of vibriosis are mild and do not require treatment.

Prevention of infection with commas

Effective infection prevention consists in:

1. After contact with potentially contaminated sea water, wash your hands thoroughly with soap and water, avoiding contamination of food, including fruit
2. We do not eat raw or undercooked shellfish. Fortunately, in the Baltic countries, food infections related to the consumption of e.g. raw oysters are rare, as our culinary tradition does not include seafood.
3. We do not swallow water while swimming in the sea
4. We also avoid contact of wounds, cuts and even scratches with sea water; before entering the sea, we cover them with a waterproof plaster or protect them with a waterproof dressing
5. Bathers must remember to keep their wounds hygienic, washing them with soap and water and disinfecting them with disinfectants.
6. Injuries that occur while collecting and preparing raw seafood and sea fish can be particularly dangerous, especially if they have come into direct contact with the wound
7. In case of any symptoms of the disease, let the doctor know about it

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