Autoclaved but not safe: Persistence of blaCTX-M and blaTEM genes encoding extended spectrum β-lactamase in autoclaved microbiological waste destined for municipal sewage disposal in Mwanza, Tanzania

Antimicrobial resistance (AMR) is a growing global public health threat, and effective treatment of microbiological waste is essential in preventing the spread of resistance genes into the environment. Autoclaving is commonly used in healthcare and laboratory settings to sterilize microbiological waste, ensuring the destruction of viable bacteria. However, the fate of antimicrobial resistance genes (ARGs), such as bla CTX-M and bla TEM , following autoclaving is not well understood. To fill this critical gap, this study determined the PCR stability of AMR encoding genes from autoclaved microbiological waste in Mwanza, Tanzania. A laboratory-based experimental study was conducted between May and August 2024 at the Catholic University of Health and Allied Sciences (CUHAS). Standard and resistant E. coli strains carrying bla CTX-M and bla TEM genes were subjected to autoclaving at 121°C and 0.1 MPa with varying duration. Bacterial viability was assessed through sub-culturing on MacConkey agar, while the presence of ARGs was evaluated using multiplex PCR. Although autoclaving eliminated culturable bacteria, PCR amplification still detected fragments of blaCTX-M and blaTEM after 30 minutes. PCR detection demonstrates amplifiable DNA fragments only, not plasmid integrity or transfer potential. These findings highlight the persistence of ARGs in treated waste and call for a re-evaluation of current bio-safety protocols.