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Solid-liquid partitioning of antibiotic-resistant bacteria and antibiotic resistance genes in wastewater
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Resumo(s)
According to the World Health Organization, Antimicrobial Resistance (AMR) is one of the greatest threats to public health. Wastewater treatment plants (WWTPs) are relevant disseminators, as they cannot completely remove micropollutants. This study evaluated the solid-liquid partitioning of antibiotic-resistant bacteria (ARBs) and antibiotic resistance genes (ARGs) and the removal efficiency of WWTPs. Escherichia coli isolates were obtained from four WWTPs, followed by antibiograms and real-time PCR for ARG detection. ARBs were more prevalent in sludge (81 %), but with lower ARG prevalence (the most common gene was found in 50 % of the isolates), suggesting other unexploited resistance mechanisms. Prevalence of ARBs and ARGs increased after secondary treatment, leading to their persistence in treated wastewater. UV radiation (used in the disinfection stage and resulting in the tertiary effluent) did not fully eliminate these micropollutants, as some ARBs and ARGs even showed increased prevalence. Reclaimed water analysis from two plants (WWTPs III and IV) revealed significant differences. WWTP sample III showed higher ARBs counts (nine resistant out of thirteen isolates) and greater ARG prevalence, including resistance to carbapenems and tigecycline compared to WWTP IV. These results indicate that operational factors, such as UV dosage (used for treatment) and organic load might affect inactivation efficiency. Thus, reclaimed water from WWTP III may contribute more to AMR dissemination than water from WWTP IV. Overall, WWTPs processes reduced the proportion of certain ARBs and ARGs, but performance varied between plants, likely influenced by the characteristics of the wastewater, operating conditions and microbial communities associated to the biological treatment. Importantly, both treated wastewater and reclaimed water sill contained significant levels of ARBs and ARGs, potentially contributing to the environmental dissemination of resistome. Therefore, it is crucial to improve wastewater treatment methods to enhance ARB and ARG removal, mitigating the spread of AMR.
Descrição
Tese de mestrado, Microbiologia Aplicada, 2025, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Antimicrobial resistance antibiotics resistance wastewater treatment plants antibiotic-resistant bacteria antibiotic resistance genes