Antimicrobial Stewardship in Hospitals, Resistance Selection and Transfer in a One Health Context (STRESST)

Wastewater is an important source of antimicrobial residues and antimicrobial-resistant (AMR) bacteria, particularly around hospitals.

Aim

The STRESST project investigated the long-term effects of hospital wastewater at Queen Elizabeth Central Hospital (QECH) in Malawi.

Results

Chemical and microbiological analyses identified the wastewater as a hotspot for AMR bacteria, likely driven by the widespread presence of antimicrobial residues. Phenotypic resistance was supported by whole-genome sequencing, which also revealed clonal relationships among isolates, suggesting bacterial persistence and growth within the wastewater system. 

In vitro models of the chicken gut and wastewater pipes were developed to study the activity of mobile genetic elements (MGEs) involved in AMR gene transfer. MGEs were more active under anaerobic conditions and in the presence of antimicrobial residues, highlighting the importance of reducing antimicrobial discharge into wastewater to limit the spread of AMR.