Longitudinal surveillance of Klebsiella pneumoniae and plasmid-mediated AmpC genes in wastewater from a treatment plant in South Africa

Background:This study investigated the temporal occurrence of Klebsiella pneumoniae and six plasmid AmpC β-lactamase gene families in wastewater from a selected wastewater treatment plant (WWTP) in South Africa, as a preliminary contribution to environmental antimicrobial resistance (AMR) surveillance. Methodology: Over 12 sampling events conducted between November 2020 and November 2021, quantitative PCR and physicochemical analyses were used to assess K. pneumoniae and the bla ACC , bla CIT , bla DHA , bla EBC , bla FOX and bla MOX gene targets in influent and final effluent. Sampling was constrained by COVID-19 restrictions, and the study was limited to one WWTP. Results:The targets showed temporal variation, with estimated influent-to-effluent reductions ranging from 6.0% to 98.2% for K. pneumoniae and from 1.3% to 99.9% for the AmpC gene targets where reductions could be calculated. However, target detection in wastewater DNA does not establish plasmid localisation or confirm that the detected AmpC genes were carried by K. pneumoniae . Correlation analyses showed some positive associations among gene targets, but these findings do not demonstrate genetic co-localisation or plasmid mobility. Although physicochemical parameters were examined, correlations involving K. pneumoniae were not statistically significant. Comparison with National Institute for Communicable Diseases (NICD) clinical data provided contextual information on reported clinical resistance patterns but did not establish a direct epidemiological link between clinical and wastewater findings. Conclusion: Overall, this pilot study demonstrates the feasibility of monitoring K. pneumoniae and selected pAmpC gene targets in wastewater, while highlighting the need for larger, multi-site studies incorporating additional ESKAPE pathogens, established microbial and AMR indicators, isolate-based characterisation, and clinical–environmental comparisons. Such studies are needed to determine whether K. pneumoniae can provide reliable sentinel information for environmental AMR surveillance in South Africa.