Effects of Sulfamethoxazole on Growth and Antibiotic Resistance of A Natural Microbial Community

Application of the Aliivibrio fischeri bacterium bioassay for assessing single and mixture effects of antibiotics and copper

The Aliivibrio fischeri bioassay was successfully applied in order to evaluate the acute effect of sulfamethoxazole (SMX), ciprofloxacin (CIP), chlortetracycline (CTC) and copper (Cu), alone or in binary, ternary, and overall mixture. The toxicity results are reported in terms of both effective concentrations, which inhibited 50% of the bacterium bioluminescence (EC50%), and in Toxic Units (TUs). The TUs were compared with predicted values obtained using the Concentration Addition model (CA). Finally, the toxicity of water extracts from a soil contaminated by the three antibiotics (7 mg Kg-1 each) in the presence/absence of copper (30 mg Kg-1) was also evaluated. Copper was the most toxic chemical (EC50: 0.78 mg L-1), followed by CTC (EC50: 3.64 mg L-1), CIP (96 mg L-1) and SMX (196 mg L-1). Comparing the TU and CA values of the mixtures, additive effects were generally found. However, a synergic action was recorded in the case of the CIP+Cu co-presence and antagonistic effects in the case of CTC+Cu and the ternary mixture (containing each antibiotic at 0.7 mg L-1), were identified. Soil water extracts did not show any toxicity, demonstrating the buffering ability of the soil to immobilize these chemicals.

Antibiotic removal potential for low greenhouse gas emission process of anaerobic digestion (AD) producing volatile fatty acids (VFAs)

This study aimed to investigate the antibiotic of sulfachloropyridazine (SCP) reduction and its effects on volatile fatty acids (VFAs) accumulation and microbial community structures during the process of anaerobic digestion (AD) producing VFA. Results showed that initial SCP concentrations have a positive correlation with reduction of SCP and accumulation of VFAs. The removal rates of SCP were 22.21%, 30.00%, 39.31% and 42.59% and the maximum production of VFAs were 3947, 6180, 6462 and 6032 mg/L for initial SCP concentrations of 25, 50, 75 and 100 mg/kg·TS, respectively. SCP only altered bacterial composition by hastening growth of specific bacterial taxa, but didn't increase bacterial α-diversity.

Antimicrobial Resistance in Rivers: A Review of the Genes Detected and New Challenges

River ecosystems are very important parts of the water cycle and an excellent habitat, food, and drinking water source for many organisms, including humans. Antibiotics are emerging contaminants which can enter rivers from various sources. Several antibiotics and their related antibiotic resistance genes (ARGs) have been detected in these ecosystems by various research programs and could constitute a substantial problem. The presence of antibiotics and other resistance cofactors can boost the development of ARGs in the chromosomes or mobile genetic elements of natural bacteria in rivers. The ARGs in environmental bacteria can also be transferred to clinically important pathogens. However, antibiotics and their resistance genes are both not currently monitored by national or international authorities responsible for controlling the quality of water bodies. For example, they are not included in the contaminant list in the European Water Framework Directive or in the US list of Water-Quality Benchmarks for Contaminants. Although ARGs are naturally present in the environment, very few studies have focused on non-impacted rivers to assess the background ARG levels in rivers, which could provide some useful indications for future environmental regulation and legislation. The present study reviews the antibiotics and associated ARGs most commonly measured and detected in rivers, including the primary analysis tools used for their assessment. In addition, other factors that could enhance antibiotic resistance, such as the effects of chemical mixtures, the effects of climate change, and the potential effects of the coronavirus disease 2019 pandemic, are discussed. Environ Toxicol Chem 2022;41:687-714. © 2022 SETAC.

Oxidation of Sulfamethoxazole by Rice Husk Biochar-Activated Persulfate

In the present study, biochars from rice husk were synthesized via pyrolysis at 400, 550, 700 and 850 °C for 1 h under a limited O2 atmosphere, characterized with a various techniques of and used as catalysts to activate persulfate and to degrade sulfamethoxazole (SMX). After physicochemical characterization of biochars. SMX degradation tests were performed using different water matrices, persulfate biochar and SMX concentrations and different initial pH solutions. Also, spiked solutions with bicarbonate, chloride, calcium nitrate, humic acid or alcohols were tested. It was found that catalytic reactivity rises with the pyrolysis temperature. Biochar is crucial for the oxidation of SMX and it can be described with a pseudo first–order kinetic model. Real matrices hinder the oxidation process, in waste water the SMX removal is 41% in 90 min, comparable with the inhibition obtained with spiked with bicarbonates solution (52% removal within 90 min) while complete removal can be achieved in ultrapure water matrices. The presence of alcohol slightly inhibits degradation contrary to the addition of sodium azide which causes significant inhibition, this is an evidence that degradation either under electron transfer/singlet oxygen control or dominated by surface-bound radicals.