Microbial Persistence in Circular Waste Streams: The Case of Enterococcus faecium in Treated Bio solids

The rapid expansion of urban infrastructure and wastewater treatment facilities has led to an unprecedented increase in the generation of sewage sludge worldwide. While treated sludge, or biosolids, is commonly repurposed as fertilizer or soil conditioner, its microbial content remains a critical area of concern, particularly the presence of persistent, multidrug-resistant bacteria such as Enterococcus faecium. This study aimed to isolate and characterize E. faecium from post-treatment biosolids and investigate its ecological adaptability and environmental persistence. Using selective culture methods and molecular identification, we confirmed the presence of strain PG (GenBank: PV413393.1) in digested, dewatered, and dried sludge samples.Ecological investigations revealed that E. faecium exhibits remarkable resilience, withstanding desiccation, ultraviolet radiation, pH fluctuations, and multiple antibiotic classes. Biofilm formation, surface adhesion, and the ability to survive in both aerobic and anaerobic conditions contribute to its persistence. Additionally, genomic traits and mobile genetic elements provide the capacity for horizontal gene transfer, enabling the spread of antimicrobial resistance within environmental microbial communities. Environmental pathways for dissemination include land application of biosolids, runoff into water bodies, aerosolization during handling, and persistence in sediments and soils.The survival and ecological versatility of E. faecium in sludge-treated environments position it as a potential reservoir and vector for antimicrobial resistance genes, with implications for soil health, water quality, and public health. These findings emphasize the need for integrated biosolid management approaches that include ecological risk assessment, targeted treatment enhancements, and continuous microbial surveillance. Balancing the benefits of organic waste recycling with the imperative of minimizing environmental and health risks will be essential in sustainable waste management strategies.