Microbiological information in the precipitate and supernatant fractions after wastewater centrifugation—loss or profit for hygiene, epidemiology, and environmental surveillance?

Objectives Wastewater-based bio-surveillance is essential for monitoring pathogens in communities. This study examines whether supernatant and the sediment left after centrifuging sewage should be tested separately or together. The goal is to assess how useful sediment information is for making accurate public health decisions. Materials and methods Total nucleic acids were isolated from wastewater inflows and outflows in Warsaw, including contributions from healthcare facilities, the airport, and residential areas, to detect SARS-CoV-2, ESKAPE pathogens, re-emerging pathogens, alarming pathogens, drug-resistance patterns, and pathotypes during two consecutive waves of COVID-19. Total DNA was extracted from both sewage water and solid phases using vacuum pressure and semi-automated methods. This DNA was then amplified using RT-qPCR and qPCR in in vitro diagnostic (IVD) tests. The analysis focused on the presence of E, N1, and N2 markers for SARS-CoV-2, sequences indicating pathotypes (such as stx , eae , ipaH , elt , and est ), and genome determinants of antibiotic resistance genes in bacteria (including van , bla , mec , SA442/CoA, SCCmec-orfX, and mcr ). Results A two-year study involving 80 locations in an urban catchment revealed both qualitative and quantitative differences in the phases following centrifugation of nearly 1,000 sewage samples. In 350 grams of sediment and over 60 micrograms of various TNA fractions, we observed frequent positive results in the sediments, while these results were absent in the supernatant (19:7). Conclusion The careful consideration of post-centrifugation phases simplifies probe selection methods, enhances the accuracy of epidemiological inferences, and enables effective responses to public health challenges, whether during normal operations or times of crisis. Additionally, quickly and accurately determining the approximate number of infected individuals can help prevent the manipulation of epidemiological data.