Comparative analysis of the pathogenic potential of bacterial isolates of the Enterobacteriaceae family isolated from wastewater and surface waters after wastewater treatment plants in Moscow

Introduction. Untreated wastewater poses a significant threat to public health and the environment. Not all treatment facilities are equally effective.

Purpose of the study. Comparison of the pathogenic potential of bacterial isolates of the Enterobacteriaceae family isolated from wastewater and surface water after treatment facilities (TF) in Moscow.

Materials and methods. Water samples were collected at the TF (inlet, post-treatment, and discharge) and from surface waters (upstream and downstream of the TF discharge point). Studies were conducted at Moscow’s TF: Zelenograd Wastewater Treatment Plant (ZWTP), Yuzhnoye Butovo Wastewater Treatment Plant (YUBOTWTP), Lyubertsy Wastewater Treatment Plant (LOS), and Kuryanovsk Wastewater Treatment Plant (KOS). PCR was used to detect potentially pathogenic determinants.

Results. Isolates recovered from the analyzed water samples at the TF were established to have a higher pathogenic potential than isolates isolated from feces (F). Antibiotic resistance genes were found in 7.5% of E. coli isolates isolated only from the TF. Pathogenic determinants were significantly more common in isolates from the TF (mrkD and CFU for Klebsiella, aggR and ipaH for E. coli). All stations reduced the number of isolates after the treatment cycle (2–11 times for E. coli and 2–4 times for Klebsiella), except for YUBOS, where the number of Klebsiella isolates decreased by only 15%, while E. coli even increased by 14%.

Limitations. We studied isolates of the Enterobacteriaceae family from Moscow TF and human feces (F) from the genus Klebsiella (157 wastewater and 117 F isolates) and Escherichia coli (100 wastewater and 80 F isolates), which represents a sufficient reference sample.

Conclusion. Overall, bacterial isolates of the Enterobacteriaceae family have been isolated from wastewater (including untreated wastewater) from Moscow’s wastewater treatment plants (WWTPs) and have a higher pathogenic potential than isolates recovered from human feces. Furthermore, water treatment at Moscow’s wastewater treatment plants (except for the YUBOTWTP) has been shown to reduce the level of bacterial contamination of wastewater by Enterobacteriaceae by four orders of magnitude. However, no reduction in pathogenic potential has been observed in viable isolates recovered from the discharge channel or from surface waters downstream of the WWTPs discharge.

Compliance with ethical standards. The study of biological material from humans was approved by the Local Independent Ethics Committee (Minutes No. 98A of the meeting of the Local Independent Ethics Committee of the National Medical Research Center of Coloproctology named after A.N. Ryzhikh, dated 07/16/2018).

Contribution.
Pay G.V. – research concept and design, experimental work, statistical processing, text writing, editing;
Kurbatova I.V. – collection and processing of samples, bacterial cultivation;
Novozhilov K.A. – collection and processing of samples, bacterial cultivation;
Mania T.R. – collection of material, editing;
Yudin S.M. – editing, approval of the final version of the article;
Zagainova A.V. – concept and design of the study, editing, approval of the final version of the article.
All authors are responsible for the integrity of all parts of the manuscript and approval of the manuscript final version.

Conflict of interest. The authors declare no conflict of interest.

Funding. The study was conducted as part of the research project “Development of standardized methods, including sampling, for determining microbiological and parasitological contamination of wastewater.” State contract No. 2123388100152000000000000/145.001.216 (code “Wastewater”), November 12, 2021.

Received: February 18, 2025 / Revised: April 25, 2025 / Accepted: June 26, 2025 / Published: December 19, 2025

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