Bacteria belonging to the Vibrio genus have been detected in water samples from Greece’s Asopos River, raising concerns about water quality and potential risks to public health, according to research by the Panhellenic Center for Ecological Research (PAKOE).
The organization reported positive results at five of the 12 locations it examined, including sites in Oinofyta, Sykamino and near the river’s mouth. The Vibrio genus includes Vibrio cholerae, the bacterium responsible for cholera, as well as other species associated with gastrointestinal illness and serious infections.
However, the findings do not establish that the cholera-causing species was present in the samples. PAKOE reported identifying bacteria from the Vibrio genus based on their growth and colony characteristics in laboratory tests.
The organization called on residents and municipal authorities to take protective measures, clean affected areas and inspect wastewater discharges, particularly outlets carrying septic waste.
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“Municipal authorities must also immediately clean the sites and inspect discharges from septic-waste pipelines. This is an extremely dangerous issue,” PAKOE said in its announcement.
What the laboratory tests found
PAKOE said its study examined water samples collected from selected locations along the Asopos River. Samples were placed in sterile 250-milliliter bottles, kept refrigerated during transport and delivered to the organization’s microbiology laboratory within six hours of collection.
Researchers used a selective laboratory medium to identify bacterial colonies associated with the Vibrio genus. The medium can produce yellow colonies when bacteria ferment sucrose and green colonies when they do not.
According to the results, five of the 12 sampling sites showed growth consistent with Vibrio bacteria.
The positive locations were:
- Two sites in Oinofyta: Both produced yellow and green colonies.
- A third site in Oinofyta: Green colonies were detected.
- Sykamino: Green colonies were detected near the bridge.
- Oropos: Green colonies were detected at a site along the river and at its mouth in Skala Oropos.
The remaining seven sampling locations tested negative for growth on the selective medium, including sites in Oropos and at the nearby Chalkoutsi beach.
PAKOE said the yellow and green colonies indicated the presence of bacteria with different laboratory characteristics. It listed Vibrio cholerae and Vibrio alginolyticus among the possible species associated with yellow colonies, and Vibrio parahaemolyticus and Vibrio vulnificus among those associated with green colonies.
These results are preliminary identification findings based on colony characteristics; the report does not establish the precise species present at each positive site.
Concerns Over Industrial Pollution
PAKOE said the Asopos River is affected by industrial pollution, including hexavalent chromium and other heavy metals, as well as agricultural runoff and wastewater discharges.
The organization warned that warmer temperatures linked to climate change may encourage Vibrio bacteria to multiply, particularly during summer. It also said industrial pollution, groundwater over-extraction and saltwater intrusion near the river’s mouth could create conditions that favor their presence.
Potential Public Health Risks
Some Vibrio bacteria can cause serious illness. Vibrio cholerae causes cholera and spreads through contaminated food or water, while Vibrio vulnificus can cause severe wound and bloodstream infections. Vibrio parahaemolyticus is linked to gastrointestinal illness, particularly from raw or undercooked seafood.
PAKOE also warned that heavy metal pollution may contribute to antibiotic resistance, although its study did not include specific test results confirming resistance in the samples.
Precautions and Calls for Action
PAKOE called on local authorities to inspect wastewater outlets and improve sanitation around the Asopos River.
The organization recommends avoiding raw or undercooked shellfish, keeping wounds away from seawater and brackish water, and washing any exposed wounds immediately with clean water and soap. People with liver disease, diabetes, kidney disease or weakened immune systems may face a higher risk of severe infection.
PAKOE stressed that clean water, proper wastewater management and good personal hygiene are essential to reducing the risk of infection.