It has been almost 30 years since the term ‘emerging contaminants’ was first used to describe contaminants that are not regulated or commonly monitored, but are known to cause adverse health effects either to humans or the ecology. These contaminants are not necessarily newly developed compounds, but their presence may have only recently begun to be investigated due, in part, to recent advances in analytical instruments which have enabled the detection of trace levels of contaminants. Over the years, contaminants of emerging concern have included pharmaceuticals and personal care products, natural and synthetic hormones, surfactants, perfluorinated compounds, plasticisers, brominated flame retardents, microplastics, etc. The issue is constantly evolving as so called ‘emerging’ compounds fall off the radar screen and new ones rapidly take their place. In this talk, I will discuss two challenging problems, that of antimicrobial resistance and harmful algal blooms and their associated contaminants of emerging concern.
The emergence of antimicrobial resistance has drawn global concerns on the ramifications in the treatment of bacterial infections. Over the years, this has led to reduced clinical efficacy in the antibiotic treatment of hospital-acquired infections due to microorganisms developing resistance mechanisms to these antimicrobial agents. Before COVID-19 took center stage, WHO had already highlighted the rapidly growing public health threat of AMR and the dangers of it spreading through the overuse and misuse of antibiotics in both the public health and animal/agricultural sectors. This problem is further complicated by the fact that antibiotic resistant bacteria and their resistant genes are able to spread to other bacteria in the environment, and vice-versa. Solving the AMR problem thus requires a One Health approach that involves a holistic understanding of the AMR contribution from the ‘environment’. Our work seeks to understand the spread of AMR and the links between antimicrobials, the human/animal populations and the environment, including through horizontal gene transfer between pathogens and environmental bacteria. We established a suite of microbiological and chemical analytical techniques to assess the antibiotic resistant bacteria (ARB), antibiotic resistant genes (ARGs) and antibiotics/antimicrobials in water and sediments within different components of the urban water cycle, including: (i) phenotypic analysis via culture based methods and antibiotic susceptibility testing, (ii) molecular analysis such as qPCR, high-throughput qPCR and metagenomics, and (iii) chemical analysis using liquid chromatography with mass spectrometry in tandem (LC-MS/MS) for targeted analysis, as well as LC-QTOF for untargeted analysis. To date, we have established a comprehensive AMR baseline dataset, comprising chemical (antibiotics and antimicrobials) and microbiological (ARB, ARGs) determinants in wastewaters, catchments, reservoirs, water and wastewater treatment plants, veterinary and wildlife facilities, aquaculture and seawater environments. Such data enable us to identify hotspots of antimicrobial resistance as well as the antimicrobials, ARB and ARGs that are of particular concern, such as those resistant to last resort antibiotics and those on the WHO priority pathogen list. In addition, the environmental baseline data gives us a reference from which we can compare future trends as the AMR situation evolves with time. We also use these data to develop models for assessing the relative risks from different hotspot areas and to predict the impacts on the health of the population. Ultimately, these risk assessment models can be used to assist regulators and policy makers to better manage antibiotics and thus, curb the spread of antibiotic resistance.