Simultaneous Determination of Seven Antibiotics and Five of Their Metabolites in Municipal Wastewater and Evaluation of Their Stability under Laboratory Conditions

Significant differences in usage of antibiotics in three Chinese cities measured by wastewater-based epidemiology

Antibiotic use, particularly inappropriate use by irrational prescribing or over-the-counter purchases, is of great concern for China as it facilitates the spread of antibiotic resistances. In this study, we applied wastewater-based epidemiology (WBE) to monitor the total consumption of eight common antibiotics in three cities in northern, eastern and southern China. Wastewater samples were successively collected from 17 wastewater treatment plants including weekdays and weekends spanning four seasons between 2019 and 2021. The concentration of antibiotics and their corresponding metabolites showed a significant correlation, confirming the measured antibiotics were actually consumed. Different seasonal trends in antibiotic use were found among the cities. It was more prevalent in the winter in the northern city Beijing, with the high antibiotic consumption attributed to peak influenza occurrence in the city. This is clear evidence of irrational prescription of antibiotics since it's known that antibiotics do little to treat influenza. In terms of overall consumption, Foshan is significantly lower, thanks to warmer climate and higher use of herbal tea as a prevention measure. WBE estimates of antibiotic consumption were relatively comparable with other data sources, with azithromycin as the top antibiotic measured here. The studied cities had higher WBE estimated antibiotics consumption than results of previous studies in the literature. Monitoring antibiotic use in different areas and periods through WBE in combination with complementary information, can better inform appropriate antibiotic guideline policies in various regions and nations.

Novel, alternative analytical methodology for determination of antimicrobial chemicals in aquatic environments and public use assessment: Extraction sorbent, microbiological sensitivity, stability, and applicability

BACKGROUND

Assessing antimicrobial chemicals from wastewater source to recipient water systems is crucial in planning effective, policy-related interventions for antimicrobial resistance (AMR) risk mitigation. However, the capability of related analytical methods for AMR assessment has not been explored previously. There is also a lack of knowledge on the effectiveness of alternative extraction sorbents with ion-exchange functions, and little information on chemical stability from sampling to analysis as well as preservative options. Hence, our study aims to address the clear need for advanced, broad-range and microbiologically-sensitive methodologies, paired with thorough stability assessments.

RESULTS

Oasis® WCX ion-exchange was for the first time employed in solid-phase extraction (SPE) for antibacterials, antifungals, antivirals and human metabolites in various water matrices. Analysis was performed using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) on a biphenyl analytical column. The optimized and validated method provided satisfactory accuracy, precision, and recovery for 53 compounds via LC-MS/MS direct injection and for up to 35 compounds via SPE-LC-MS/MS. Method quantification limits (MQLs) were determined in groundwater (0.33-54 ng L-1), surface water (0.53-75 ng L-1), effluent wastewater (2.5-470 ng L-1), and influent wastewater (11-650 ng L-1). As a novel approach, MQLs were compared with minimum inhibitory concentrations, to confirm our method's microbiological sensitivity for studying AMR. Stability assessment revealed that most compounds remained stable in standard solution at -80 °C for six months, in various waters at -20 °C for eight weeks, and during 24-h sampling at 4 °C. Sodium azide was a better preservative than sodium metabisulfite.

SIGNIFICANCE

Our study is an added value to the analytical methodology for water measurements of antimicrobial chemicals, in which it provides a novel, alternative method that is robust and overall more sensitive than others using generic Oasis® HLB sorbents and C18 analytical columns in SPE-LC-MS/MS. Also, the comprehensive data on antimicrobial stability helps reduce methodological uncertainty for future studies. Our method shows sufficient microbiologically-sensitivity and thus is suitable for future (inter)national regulatory water monitoring of AMR.

Direct injection liquid chromatography-tandem mass spectrometry as a sensitive and high-throughput method for the quantitative surveillance of antimicrobials in wastewater

Environmental antimicrobial pollution and antimicrobial resistance pose a threat to environmental and human health. Wastewater analysis has been identified as a promising tool for antimicrobial monitoring and the back-estimation of antimicrobial consumption, but current pretreatment methods are tedious and complicated, limiting their scope for high-throughput analysis. A sensitive direct injection method for the quantification of 109 antimicrobials and their metabolites in wastewater samples was developed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The method was validated for both wastewater influent and effluent in terms of specificity, calibration range, matrix effect, filtration loss, accuracy, precision, limit of detection (LOD), and limit of quantification (LOQ). Most analytes achieved calibration of R2 > 0.99, and the calibration range was from 0.0002 to 150 μg L-1. Recoveries ranged consistently between ~50 % and ~100 % and losses were attributed to sample filtration. Method LOQs were determined as low as 0.0003 μg L-1, and acceptable accuracy (75 %-125 %) and precision (within 25 %) were achieved for >90 % of the analytes. The method was subsequently further assessed using wastewater of raw influent and treated effluent collected from 6 Australian wastewater treatment plants in 2021. In total, 37 analytes were detected in influent and 22 in effluent. Most of them could be quantified at concentrations ranging from 0.0053 to 160 μg L-1, with benzalkonium chloride-C12, amoxicilloic acid, and cephalexin detected at the highest concentrations. The current study provides a straightforward analytical method for antimicrobial monitoring in wastewater with a fast and simple pretreatment procedure.

Occurrence, removal, emission and environment risk of 32 antibiotics and metabolites in wastewater treatment plants in Wuhu, China

Wastewater treatment plants (WWTPs) are considered important sources of antibiotics and metabolites in aquatic environments and pose a serious threat to the safety of aquatic organisms. In this study, we investigated the seasonal occurrence, removal, emission, and environmental risk assessment (ERA) of 32 antibiotics and metabolites at four WWTPs located in Wuhu, China. The main findings of this study are as follows: Ofloxacin concentrations dominated all WWTPs, and large quantities of sulfachinoxalin were only detected in WWTP 2 treating mixed sewage. The average apparent removal of individual parent antibiotics or metabolites ranged from -94.7 to 100 %. There was a noticeable seasonal emission pattern (independent t-test, t = 9.89, p < 0.001), with lower emissions observed during summer. WWTPs discharged 85.2 ± 43.8 g of antibiotics and metabolites each day. Approximately 87 % of emissions were discharged into the mainstream of the Yangtze River, while the remainder were discharged into its tributary, the Zhanghe River. The total emissions of 21 parent antibiotics were approximately 18 % of the prescription data, indicating that a considerable and alarming amount of prototype drugs entered the receiving water body. Based on the risk quotient (RQ) of the ERA, the Zhanghe River has a moderate risk of ofloxacin (RQ = 0.111-0.583), a low or insignificant risk of sulfamethoxazole (RQ = 0.003-0.048), and an insignificant risk of other antibiotics or metabolites. However, the risk of antibiotics or metabolites in the mainstream of Yangtze River is insignificant. This study could help understand the seasonal emission patterns of antibiotics and metabolites, as well as more antibiotics sensitive of environmental risks in tributary than that in mainstream.

Analytical key issues and challenges in the LC-MS/MS determination of antibiotics in wastewater

The research on antibiotics occurrence in the aquatic environment has become a hot topic in the last years due to their potential negative effects, associated to possible bacterial antibiotic-resistance, after continuous exposure to these compounds. Most of antibiotic residues are not completely removed in the wastewater treatment plants (WWTPs) and end up in the aquatic environment through treated wastewater (WW). The development of reliable analytical methodologies for the determination of antibiotics in influent (IWW) and effluent wastewater (EWW) is needed with different purposes, among others: monitoring their occurrence in the aquatic environment, performing environmental risk assessment, estimating removal efficiencies of WWTPs, or estimating the consumption of these compounds. In this paper, we perform an in-depth investigation on analytical key issues that pose difficulties in the determination of antibiotics in complex matrices, such as WW, and we identify challenges to be properly addressed for successful analysis. The analytical technique selected was liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS), as it is the most powerful and widely applied at present for antibiotic residues determination. The mass spectrometric behavior of 18 selected antibiotics, the chromatographic performance, ion ratio variations associated to the sample matrix when using different precursor ions or protomers, and the macrolides adsorption to glass vial, were some of the issues studied in this work. On the basis of the detailed study performed, an analytical LC-MS/MS method based on sample direct injection has been developed for quantification of 18 antibiotics in IWW and EWW, allowing their determination at low ng L^-1 levels.

Biomarker selection strategies based on compound stability in wastewater-based epidemiology

The specific compositions of human excreta in sewage can be used as biomarkers to indicate the disease prevalence, health status, and lifestyle of the population living in the investigated catchment. It is important for guiding and evaluating public health policies as well as promoting human health development. Among several parameters of wastewater-based epidemiology (WBE), the decay of biomarkers during transportation in sewer and storage plays a crucial role in the back-calculation of population consumption. In this paper, we summarized the stability data of common biomarkers in storage at different temperatures and in-sewer transportation. Among them, cardiovascular drugs and antidiabetic drugs are very stable which can be used as biomarkers; most of the illicit drugs are stable except for cocaine, heroin, and tetrahydrocannabinol which could be substituted by their metabolites as biomarkers. There are some losses for part of antibiotics and antidepressants even in frozen storage. Rapid detection of contagious viruses is a new challenge for infectious disease control. With the deeper and broader study of biomarkers, it is expected that the reliable application of the WBE will be a useful addition to epidemiological studies.

Inactivation of Bacteria and Residual Antimicrobials in Hospital Wastewater by Ozone Treatment

The emergence and spread of antimicrobial resistance (AMR) has become a persistent problem globally. In this study, an ozone treatment facility was established for an advanced hospital wastewater treatment in a core hospital facility in an urban area in Japan to evaluate the inactivation of antimicrobial-resistant bacteria and antimicrobials. Metagenomic DNA-seq analysis and the isolation of potential extended-spectrum β-lactamase (ESBL)-producing bacteria suggested that ozone exposure for at least 20 min is required for the adequate inactivation of DNA and ESBL-producing bacteria. Escherichia coli and Klebsiella species were markedly susceptible to 20-min ozone exposure, whereas Raoultella ornithinolytica and Pseudomonas putida were isolated even after an 80-min exposure. These ozone-resistant bacteria might play a pivotal role as AMR reservoirs in the environment. Nine antimicrobials (ampicillin, cefdinir, cefpodoxime, ciprofloxacin, levofloxacin, clarithromycin, chlortetracycline, minocycline, and vancomycin) were detected at 373 ng/L to 27 μg/L in the hospital wastewater, and these were removed (96–100% removal) after a 40-min treatment. These results facilitate a comprehensive understanding of the AMR risk posed by hospital wastewater and provides insights for devising strategies to eliminate or mitigate the burden of antimicrobial-resistant bacteria and the flow of antimicrobials into the environment. To the best of our knowledge, this is the first report on the implementation of a batch-type, plant-scale ozone treatment system in a hospital facility to execute and evaluate the inactivation of drug-resistant bacteria and antimicrobials.

Exploring antibiotic consumption between urban and sub-urban catchments using both parent drugs and related metabolites in wastewater-based epidemiology

Consumption of antibiotics leads to the dissemination of antimicrobial resistance worldwide. Better knowledge of temporal and spatial consumption of antibiotics helps public health authorities to control their usage and combat antimicrobial resistance. However, measuring antibiotic consumption with population surveys, sales data, and production statistics remains challenging due to the complexity of prescription preference, patient compliance, and direct disposal of unused drugs. With the approach of wastewater-based epidemiology (WBE), this study aims to evaluate the consumption of eight commonly-used antibiotics between developed urban and developing sub-urban catchments in China and to characterise the ratios of parent drugs to metabolites in studying the consumption. Seven parent antibiotics were detected in all the wastewater samples (n = 56), whereas some metabolites were detected sporadically. The ratios of parent chemicals to metabolites varied among locations and were often higher than the ratios in pharmacokinetic studies. Estimated consumption of antibiotics ranged from 3.2 ± 2.0 mg/day/1000 inhabitants for trimethoprim to 28,400 ± 7800 mg/day/1000 inhabitants for roxithromycin in the studied catchments. Higher consumption of sulfapyridine, sulfadiazine and roxithromycin was observed in urban than suburban catchments, while consumption of sulfamethoxazole, norfloxacin, and trimethoprim was higher in suburban than in urban catchments. Using the literature data, we found more than 95% reduction of antibiotic use in an urban catchment. Our study revealed the geographical pattern in antibiotic use across different urban and suburban catchments via WBE, and the potential of monitoring parent-to-metabolite ratios for WBE in estimating antibiotic use. These results provide a basis for health authorities to plan different drug-specific control policies between urban and suburban catchments, and for future WBE studies to be aware of other sources, such as animal husbandry and disposals of unused drugs, that can influence the estimated consumption.

Estimating antibiotics use in major cities in China through wastewater-based epidemiology

Antibiotics have been widely used for disease treatment and may pose adverse effects on human health due to increasing presence of antibiotic-resistant genes in environment. Therefore, it is important to understand antibiotic use in a specific region or country. China is a major producer of antibiotic and has a large number of consumers. In this work, wastewater samples were collected from 76 wastewater treatment plants in 31 major cities covering all of the geographic regions of China. Concentrations of eight metabolites of sulfonamide, quinolone and macrolide antibiotics were determined. The consumption levels of corresponding antibiotics were estimated based on wastewater-based epidemiology (WBE) approach. Desmethyl ofloxacin, desethylene norfloxacin, desmethyl azithromycin and N⁴-acetyl sulfamethoxazole were detected in all or the overwhelming majority of wastewater samples. The estimated ∑8Antibiotics consumption levels ranged from 275.1 ± 139.4 mg/1000 inh/d (Nanchang) to 3860.9 ± 1332.3 mg/1000 inh/d (Harbin) with a mean level of 1170.0 ± 452.1 mg/1000 inh/d. Quinolones accounted for the highest proportion (74.3%, national average contribution) in the total consumption level, with norfloxacin being the dominant one (38.4%), followed by ofloxacin (29.1%) and ciprofloxacin (6.8%). The ∑8Antibiotics consumption level in northern China (1517.0 ± 1022.8 mg/1000 inh/d) was statistically higher than the level in southern China (1060.7 ± 989.1 mg/1000 inh/d) (t-test, p < 0.05). In contrast, no significant difference was found between eastern (1256.2 ± 1105.1 mg/1000 inh/d) and western China (988.3 ± 474.5 mg/1000 inh/d) (t-test, p > 0.05). The overview of antibiotics consumption derived from this work can serve as a baseline to assess the implementation of related plans/policies in China.

Antimicrobial Resistance Development Pathways in Surface Waters and Public Health Implications

Human health is threatened by antibiotic-resistant bacteria and their related infections, which cause thousands of human deaths every year worldwide. Surface waters are vulnerable to human activities and natural processes that facilitate the emergence and spread of antibiotic-resistant bacteria in the environment. This study evaluated the pathways and drivers of antimicrobial resistance (AR) in surface waters. We analyzed antibiotic resistance healthcare-associated infection (HAI) data reported to the CDC's National Healthcare Safety Network to determine the number of antimicrobial-resistant pathogens and their isolates detected in healthcare facilities. Ten pathogens and their isolates associated with HAIs tested resistant to the selected antibiotics, indicating the role of healthcare facilities in antimicrobial resistance in the environment. The analyzed data and literature research revealed that healthcare facilities, wastewater, agricultural settings, food, and wildlife populations serve as the major vehicles for AR in surface waters. Antibiotic residues, heavy metals, natural processes, and climate change were identified as the drivers of antimicrobial resistance in the aquatic environment. Food and animal handlers have a higher risk of exposure to resistant pathogens through ingestion and direct contact compared with the general population. The AR threat to public health may grow as pathogens in aquatic systems adjust to antibiotic residues, contaminants, and climate change effects. The unnecessary use of antibiotics increases the risk of AR, and the public should be encouraged to practice antibiotic stewardship to decrease the risk.

Evaluation of the Correspondence between the Concentration of Antimicrobials Entering Sewage Treatment Plant Influent and the Predicted Concentration of Antimicrobials Using Annual Sales, Shipping, and Prescriptions Data

The accuracy and correspondence between the measured concentrations from the survey and predicted concentrations on the basis of the three types of statistical antimicrobial use in Japan was evaluated. A monitoring survey of ten representative antimicrobials: ampicillin (APL), cefdinir (CDN), cefpodoxime proxetil (CPXP), ciprofloxacin (CFX), clarithromycin (CTM), doxycycline (DCL), levofloxacin (LFX), minocycline (MCL), tetracycline (TCL), and vancomycin (VMC), in the influent of sewage treatment plant (STP) located in urban areas of Japan, was conducted. Then, the measured values were verified in comparison with the predicted values estimated from the shipping volumes, sales volumes, and prescription volumes based on the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB). The results indicate that the correspondence ratios between the predicted concentrations calculated on the basis of shipping and NDB volumes and the measured concentrations (predicted concentration/measured concentration) generally agreed for the detected concentration of antimicrobials in the STP influent. The correspondence ratio on the basis of shipping volume was, for CFX, 0.1; CTM, 2.9; LFX, 0.5; MCL, 1.9; and VMC, 1.7, and on the basis of NDB volume the measured concentration was CFX, 0.1; CTM, 3.7; DCL, 0.4; LFX, 0.7; MCL, 1.9; TCL, 0.6; and VMC, 1.6. To our knowledge, this is the first report to evaluate the accuracy of predicted concentrations based on sales, shipping, NDB statistics and measured concentrations for antimicrobials in the STP influent.