Bacterial lineages putatively associated with the dissemination of antibiotic resistance genes in a full-scale urban wastewater treatment plant

Abstract

Urban wastewater treatment plants (UWTPs) are reservoirs of antibiotic resistance. Wastewater treatment changes the bacterial community and inevitably impacts the fate of antibiotic resistant bacteria and antibiotic resistance genes (ARGs). Some bacterial groups are major carriers of ARGs and hence, their elimination during wastewater treatment may contribute to increasing resistance removal efficiency. This study, conducted at a full-scale UWTP, evaluated variations in the bacterial community and ARGs loads and explored possible associations among them. With that aim, the bacterial community composition (16S rRNA gene Illumina sequencing) and ARGs abundance (real-time PCR) were characterized in samples of raw wastewater (RWW), secondary effluent (sTWW), after UV disinfection (tTWW), and after a period of 3 days storage to monitoring possible bacterial regrowth (tTWW-RE). Culturable enterobacteria were also enumerated. Secondary treatment was associated with the most dramatic bacterial community variations and coincided with reductions of ~2 log-units in the ARGs abundance. In contrast, no significant changes in the bacterial community composition and ARGs abundance were observed after UV disinfection of sTWW. Nevertheless, after UV treatment, viability losses were indicated ~2 log-units reductions of culturable enterobacteria. The analysed ARGs (qnrS, bla, bla, bla, bla, sul1, sul2, and intI1) were strongly correlated with taxa more abundant in RWW than in the other types of water, and which associated with humans and animals, such as members of the families Campylobacteraceae, Comamonadaceae, Aeromonadaceae, Moraxellaceae, and Bacteroidaceae. Further knowledge of the dynamics of the bacterial community during wastewater treatment and its relationship with ARGs variations may contribute with information useful for wastewater treatment optimization, aiming at a more effective resistance control.

Linking the Resistome and Plasmidome to the Microbiome

“…Overall, the results are in line with current knowledge of the taxonomic distribution of these ARGs. This technique suggests that Aeromonadaceae, Acinetobacter, and Bacteroidetes are reservoirs of ARGs in this wastewater, as also recently suggested for another wastewater sample in Portugal using different approaches [26].…”

Removal of antibiotic resistance genes in various water resources recovery facilities

“…Lee et al () also reported up to 4 log reductions of ARGs for a similarly configurated WWTP. Studies on UV disinfection show that UV treatment alone removes ARGs around 0 log reduction (Lee et al, ; Narciso‐da‐Rocha et al, ). The removal of ARGs by UV alone demonstrate a positive relationship with the dose of the UV applied (Sharma, Johnson, Cizmas, McDonald, & Kim, ).…”

“…Studies on the coagulation (coag–floc) process produce up to 3 log reductions depending on the coagulants used (Li, Sheng, Lu, Zeng, & Yu, ). Studies on UV disinfection showed that the removal efficiencies vary around 0 log reduction (Narciso‐da‐Rocha et al, ). Despite the growing attention, removal of ARGs in WWTPs and the effect of ARG type on its inactivation efficiency via different treatment processes have not been completely understood yet.…”

Immobilised Cerium-Doped Zinc Oxide as a Photocatalyst for the Degradation of Antibiotics and the Inactivation of Antibiotic-Resistant Bacteria

“…The concentrations of antibiotics for CCA were as per CLSI guidelines for Enterobacteriaceae [60]. For CET, antibiotic concentrations of ofloxacin were again as per CLSI guidelines for Pseudomonas aeruginosa while for ciprofloxacin a more environmentally relevant cut-off concentration (1 µg/mL) for resistance, which also has been previously reported, was chosen instead [61,62]. Resistance was estimated based on the ratio of the number of colonies enumerated in the presence of an antibiotic to the enumeration in its absence, using the equation below:…”