TREATED WASTEWATER: A PATHWAY FOR THE SPREAD OF KLEBSIELLA PNEUMONIAE

Wastewater treatment plants may act as critical hubs for the spread of antibiotic-resistant pathogenic bacteria. This is the key finding of a study conducted through a collaboration between the Water Research Institute (IRSA) of the National Research Council, the Experimental Zooprophylactic Institute of Teramo (IZS di Teramo), and the National Biodiversity Future Center (NBFC) of Palermo. Researchers detected the presence of the bacterium Klebsiella pneumoniae in an urban wastewater treatment plant in central Italy.

Klebsiella pneumoniae is a bacterium naturally found in the human microbiome. Certain strains cause severe respiratory, urinary, and bloodstream infections, particularly in vulnerable individuals, often in healthcare settings such as hospitals. Globally, Klebsiella pneumoniae is one of the microorganisms of greatest concern due to its resistance to numerous antibiotics, including last-resort drugs such as colistin.

The study, published in the scientific journal Environmental Pollution, analyzed samples taken from influent water, sedimentation tanks, and effluent water in an urban wastewater treatment plant. Samples collected during four distinct periods in 2018 revealed the presence of 42 Klebsiella pneumoniae strains, subsequently characterized through whole genome sequencing. Many of the isolated strains (47%) exhibited a multi-drug-resistant phenotype to at least three classes of antibiotics, with some resistant to colistin. High-risk, rapidly spreading clones such as ST307, ST35, and ST45 were also identified in Italy.

“Klebsiella pneumoniae - explains Alessandra Cornacchia, IZSAM researcher and first author of the study along with IRSA researcher Andrea Di Cesare - is among the leading causes of infections in healthcare settings. If wastewater treatment plants are not properly monitored, they can contribute to the spread of this dangerous bacterium in the environment and communities. Monitoring not only identifies the issue but also provides critical guidance for corrective actions, such as modifying plant processes, to help mitigate the spread of the phenomenon”.

While essential for water purification, wastewater treatment plants can inadvertently contribute to the dissemination of drug-resistant bacteria in aquatic ecosystems. This underscores the need for continuous monitoring of these facilities and the implementation of appropriate measures to limit the spread of pathogenic strains, ultimately protecting public health.

“Microbiological studies of wastewater - comments Francesco Pomilio, Head of the Food Hygiene and Technology Unit at IZSAM – constitutes an additional pillar of integrated health surveillance. Understanding the bacterial and viral species present in treated water and their genomic characterization is fundamental to improving treatment systems and developing innovative strategies to reduce their presence, particularly in the case of antibiotic-resistant bacteria. Only an integrated approach, considering environmental, health, and microbiological aspects, can ensure safer management of wastewater”.