What are the impacts of warming waters and environmental pollution on pathogens? If we are to plan for potential waterborne disease outbreaks, we need to better understand two things: what are the antibiotic-resistant profiles of aquatic pathogens, and what is their spread?

Stefania Marcheggiani and a team of researchers from the Istituto Superiore di Sanità (ISS) investigated pathogens in Lake Paola, a Mediterranean coastal lake. The brackish lake is a transitional body of water with channels between the land and the sea: the perfect place for pathogen loads to enter coastal waters.

Lake Paola is a busy place, used for both recreational activities and shellfish farming. In the summer, it’s a popular visitor destination. In addition, the lake is affected by climate change, with an increase in flooding, saline intrusion (salt water flowing into fresh water) and warmer temperatures.

Why is this important?

We need to improve our understanding of the relationship between climate change and the increase in bug-resistant strains of pathogens. Antimicrobial resistance (AMR) happens when bacteria evolve to stop responding to medication. This has serious implications for human health, medical treatment and infection spread.

Transitional waters – the mixing zone between fresh and salt waters – are a particularly risky place for the spread of multidrug-resistant (MDR) pathogenic bacteria and are sensitive to climate change. Surprisingly, these vulnerable environments are not subject to mandatory monitoring.

The research aimed to identify the presence and AMR profiles of pathogenic microorganisms, looking at the risk they pose to recreational activities and how the research can support One Health planning.

Research highlights

1. The spread and profiles of waterborne pathogens need to be studied in the context of climate change so we’re better prepared for the future.
2. Regular sampling at key sites will identify individual strains, their AMR profiles and their concentration in these areas.
3. The ISS team worked on developing the Potential Spreading of Pathogens (PSP) index, an invaluable tool to help with decision-making and mitigation planning.

Methodology

The team chose three sampling sites during the main bathing season of 2023. Site P1 was near the Catrattino Canal, which connects the lake to the sea. Site P2 was in the central part of the lake, next to Sabaudia village. Site P3 was near the Paola Canal, the main channel connecting the lake to the sea, which is close to the main shellfish production area.

For pathogen sampling, the team from ISS used Artificial Plastic Substrates (APSs) (see our Arrone River case study to find out more about this effective method [link]). They submerged the plastic polymer tiles at each sample site, to be collected monthly for analysis.

The monthly testing also included measuring pH, conductivity, water and air temperature, salinity and dissolved oxygen to take into account the effects of climate stressors. To identify the main human-made pressures on the lake, the team carried out land use analysis using Geographical Information System software.

From this, the PSP index incorporates and categorises the spread of pathogens at each site. To make this easy for all users, the researchers created five quality classes for pathogen dissemination: blue, green, yellow, orange and red.

Results

Results and publications coming soon…