Occurrence, Distribution, and Ecological Risk Assessment of Antibiotics in Different Environmental Media in Anqing, Anhui Province, China

Distribution of antibiotic resistance genes and antibiotic residues in drinking water production facilities: Links to bacterial community

There is a rapid spread of antibiotic resistance in the environment. However, the impact of antibiotic resistance in drinking water is relatively underexplored. Thus, this study aimed to quantify antibiotic resistance genes (ARGs) and antibiotic residues in two drinking water production facilities (NW-E and NW-C) in North West Province, South Africa and link these parameters to bacterial communities. Physicochemical and ARG levels were determined using standard procedures. Residues (antibiotics and fluconazole) and ARGs were quantified using ultra-high performance liquid chromatography (UHPLC) chemical analysis and real-time PCR, respectively. Bacterial community compositions were determined by high-throughput 16S rRNA sequencing. Data were analysed using redundancy analysis and pairwise correlation. Although some physicochemical levels were higher in treated than in raw water, drinking water in NW-E and NW-C was safe for human consumption using the South African Water Quality Guideline (SAWQG). ARGs were detected in raw and treated water. In NW-E, the concentrations of ARGs (sul1, intl1, EBC, FOX, ACC and DHA) were higher in treated water than in raw water. Regarding antimicrobial agents, antibiotic and fluconazole concentrations were higher in raw than in treated water. However, in NW-C, trimethoprim concentrations were higher in raw than in treated water. Redundancy analysis showed that bacterial communities were not significantly correlated (Monte Carlo simulations, p-value >0.05) with environmental factors. However, pairwise correlation showed significant differences (p-value <0.05) for Armatimonas, CL500-29 marine group, Clade III, Dickeya and Zymomonas genera with environmental factors. The presence of ARGs and antibiotic residues in the current study indicated that antibiotic resistance is not only a clinical phenomenon but also in environmental settings, particularly in drinking water niches. Consumption of NW-E and NW-C treated water may facilitate the spread of antibiotic resistance among consumers. Thus, regulating and monitoring ARGs and antibiotic residues in drinking water production facilities should be regarded as paramount.

Levels and ecological risk of pharmaceuticals in River Sosiani, Kenya

The continued frequent detection of pharmaceuticals in the environment is of major concern due to potential human and ecological risks. This study evaluated 30 antibiotics from 8 classes: sulphonamides (SAs), penicillins (PNs), fluoroquinolones (FQs), macrolides (MLs), lincosamides (LINs), nitroimidazoles (NIs), diaminopyrimidines (DAPs), salfones and 4 anthelmintics benzimidazoles (BZs) in surface water and sediments from River Sosiani in Eldoret, Kenya. Samples were collected during the wet and dry seasons and subjected to solid phase extraction using HLB cartridges. A liquid chromatography tandem mass spectrometry (LC-MS/MS) method was used for the simultaneous quantification of the compounds. Chromatographic separation was on a reversed-phase Zorkax Eclipse Plus C18 column eluted in a gradient program and compounds detected by mass spectrometer operated in a positive electrospray ionization (+ ESI) mode. Twenty-eight antibiotics were detected in water where 22 had a 100% detection frequency and the remaining 4 showed detection frequencies ranging from 5 to 47%. Three BZs had a 100% detection frequency. Detectable concentrations of the pharmaceuticals in water ranged between 0.1 and 247 ng L^-1 and 0.01 and 974 µg kg^-1 in the sediments. The sulfonamide, sulfamethoxazole, had the highest concentration in water (247 ng L^-1), whereas penicillin G showed the highest concentrations in sediments (414-974 µg kg^-1). Quantified pharmaceuticals decreased in the order SAs > DAPs > FQs > ATs > PNs ≈ MCs ≈ LNs > NIs in water, and followed the order PNs > BZs > FQs > MLs > DAPs ≈ LNs > NIs > SAs in sediments. Risk quotients (RQ_w) showed that sulfamethoxazole and ciprofloxacin were of high ecological risk in the surface water (RQ_w values of 1.11 and 3.24, respectively), whereas penicillin V, ampicillin, penicillin G, norfloxacin, enrofloxacin, erythromycin, tylosin, and lincomycin were of medium ecological risk in the aquatic system. The findings show high prevalence of pharmaceuticals in surface water and sediments and are therefore potential ecological hazards. Such information is vital when devising mitigation strategies.

Seasonal variability of the correlation network of antibiotics, antibiotic resistance determinants, and bacteria in a wastewater treatment plant and receiving water

Sewage treatment plants are an essential source of antibiotics, antibiotic resistance determinants, and bacteria in environmental waters. However, it is still unclear whether they can maintain a relatively stable relationship in wastewater and environmental waters. This study analyzed the removal capacity of the above three pollutants in the sewage treatment plant in summer and their impact on environmental waters, and then examines the relationship between the three contaminants in the wastewater and environmental waters in summer and winter based on our previous study. The results found that the removal capacity of bacteria in summer was poor, the concentration of fluoroquinolone in the effluent was higher than that in influent, and the abundance of intI1, tetW, qnrB, and ermB increased after wastewater treatment. Proteobacteria and Bacteroides were the main bacteria that constitute the correlation network between bacteria, and they existed stably in summer and winter. However, fluoroquinolones occupied a significant position in the determinant network of antibiotics and antibiotic resistance in summer and winter. There are fewer correlation between antibiotics and antibiotics resistance determinants in winter. Interestingly, the relationship between bacteria, antibiotics, and antibiotic resistance determinants was a mainly positive correlation in summer and negative correlation in winter. This study analyzed the relationship between bacteria, antibiotics, and antibiotic resistance determinants that were stable in the wastewater and environmental waters and pointed out the direction for subsequent targeted seasonal control of novel pollutants in wastewater and environmental waters.

Spatial and Temporal Distribution Characteristics and Potential Risks of Sulfonamides in the Shaanxi Section of the Weihe River

The hazards of antibiotics as emerging contaminants to aquatic ecosystems and human health have received global attention. This study investigates the presence, concentration levels, spatial and temporal distribution patterns, and their potential risks to aquatic organisms and human health of sulfonamides (SAs) in the Shaanxi section of the Weihe River. The SA pollution in the Weihe River was relatively less than that in other rivers in China and abroad. The spatial and temporal distribution showed that the total concentrations of SAs in the Weihe River were highest in the main stream (ND−35.296 ng/L), followed by the south tributary (3.718−34.354 ng/L) and north tributary (5.476−9.302 ng/L) during the wet water period. Similarly, the order of concentration from highest to lowest during the flat water period was main stream (ND−3 ng/L), north tributary (ND−2.095 ng/L), and south tributary (ND−1.3 ng/L). In addition, the ecological risk assessment showed that the SAs other than sulfadiazine (SDZ) and sulfamethoxazole (SMZ) posed no significant risk (RQS < 0.01) to the corresponding sensitive species during both periods, with no significant risk to human health for different age groups, as suggested by the health risk assessment. The risk of the six SAs to both aquatic organisms and human health decreased significantly from 2016 to 2021.

Antibiotics, antibiotic-resistant bacteria, and resistance genes in aquaculture: risks, current concern, and future thinking

Aquaculture is remarkably one of the most promising industries among the food-producing industries in the world. Aquaculture production as well as fish consumption per capita have been dramatically increasing over the past two decades. Shifting of culture method from semi-intensive to intensive technique and applying of antibiotics to control the disease outbreak are the major factors for the increasing trend of aquaculture production. Antibiotics are usually present at subtherapeutic levels in the aquaculture environment, which increases the selective pressure to the resistant bacteria and stimulates resistant gene transfer in the aquatic environment. It is now widely documented that antibiotic resistance genes and resistant bacteria are transported from the aquatic environment to the terrestrial environment and may pose adverse effects on human and animal health. However, data related to antibiotic usage and bacterial resistance in aquaculture is very limited or even absent in major aquaculture-producing countries. In particular, residual levels of antibiotics in fish and shellfish are not well documented. Recently, some of the countries have already decided the maximum residue levels (MRLs) of antibiotics in fish muscle or skin; however, many antibiotics are yet not to be decided. Therefore, an urgent universal effort needs to be taken to monitor antibiotic concentration and resistant bacteria particularly multiple antibiotic-resistant bacteria and to assess the associated risks in aquaculture. Finally, we suggest to take an initiative to make a uniform antibiotic registration process, to establish the MRLs for fish/shrimp and to ensure the use of only aquaculture antibiotics in fish and shellfish farming globally.