Stability and activity of phages targeting antibiotic-resistant bacteria in wastewater

Abstract

Antimicrobial resistance (AMR) poses a significant threat to public health, with wastewater treatment plants (WWTPs) acting as reservoirs for resistant bacteria and genes. Bacteriophages, natural bacterial predators, offer a promising, targeted alternative to mitigate AMR in these environments. This study assessed how different multiplicities of infection (MOIs), and liquid matrices (nutrient-rich LB medium and wastewater) affect the activity and stability of lytic phages LM09 and HPP5 against E. coli (ECO9B) and P. aeruginosa (PAO1), respectively. Overall, results demonstrated that both phages efficacy is influenced by MOI and matrix composition, with higher MOIs yielding stronger bacterial reductions and bacterial growth delays, particularly in LB medium. However, both phages showed limited stability without a host, irrespective of the matrix. These findings underscore the potential of phages in addressing AMR in a wastewater treatment setting while highlighting the need for optimized experimental designs to enhance reproducibility and applicability in real-world scenarios.

Date of Award	23 Jun 2025
Original language	English
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Heike Schmitt (Supervisor) & Gonçalo Nuno Barroca de Macedo (Co-Supervisor)