Tracking Klebsiella pneumoniae carbapenemase gene as an indicator of antimicrobial resistance dissemination from a hospital to surface water via a municipal wastewater treatment plant.

Antibiotic-resistant bacteria originating from hospitals are ultimately discharged to municipal wastewater treatment plants (WWTP), which may serve as important reservoirs for the spread of antibiotic resistant genes. This study traced and quantified the presence of a rare but clinically relevant antimicrobial resistance gene; Klebsiella pneumoniae carbapenamase (KPC)-and the viable organisms (KPCO) which carried this gene in hospital, non-hospital wastewater discharges, various compartments within a municipal WWTP, receiving water and sediment samples. High concentration of the gene, blaKPC harbored in viable and multispecies KPCO was detected in the hospital wastewater and in the forepart stages of the WWTP, but was not detected in the final effluent following UV disinfection. KPCO were not detected in multiple non-hospital sources of wastewater discharges tested. The treatment train used in the sampled WWTP was found to help remove and reduce KPCO load. Using whole-genome sequencing, a KPC-producing Klebsiella oxytoca strain identical to strains seen in the patients and hospital environment was isolated from the downstream receiving water on one sampling event. KPCO were also found to persist in the biosolids throughout the WWTP, but were not detected in the processed compost-products made from WWTP-biosolids. This study systematically demonstrates dissemination of KPCO from hospital point source to environment via municipal WWTP. Understanding hospitals as the origin and source of spread of some of the most clinically urgent antimicrobial-resistant organisms may help direct interventions that target rate at which antibiotic resistant bacteria evolve and spread via enhancement of wastewater treatment and mitigation of dissemination at source.

Evaluating the efficacy of an algae-based treatment to mitigate elicitation of antibiotic resistance.

Antibiotics in the effluents of municipal wastewater treatment plants (WWTP) may create selective pressures to induce antibiotic resistance in bacteria downstream. This study evaluates ciprofloxacin (CIP) removal by a freshwater alga, Scenedesmus dimorphus, to assess the efficacy of algae-based tertiary treatment in reducing effluent-induced CIP resistance. Results show significant CIP removal in light-exposed samples without algae and experimental algae (EA) samples: 53% and 93%, respectively, over 144 h. A residual antibiotic potency assay reveals that untreated CIP is significantly more growth-inhibiting to a model bacterium (Escherichia coli) than the algae-treated and light-exposed samples during short exposures (6 h). Adaptive laboratory evolution (ALE), again using E. coli, reveals that treated samples exhibit reduced capacity to elicit CIP resistance during sustained exposures compared to untreated CIP. Finally, observed CIP resistance in the CIP-exposed ALE lineages is corroborated via genotype characterization, which reveals the presence of resistance-associated mutations in gyrase subunit A (gyrA) that are not present in ALE lineages exposed to algae treated or light-exposed samples. As such, algae-mediated tertiary treatment could be effective in suppressing CIP resistance in bacterial communities downstream from WWTP. In addition, ALE is useful for assessing the potential of wastewater-relevant samples to elicit antibiotic resistance downstream.