Integrity of bacterial genomic DNA after autoclaving: possible implications for horizontal gene transfer and clinical waste management.

Current autoclaving practices are designed to kill bacteria. Little is known about the effect of autoclaving on the integrity of bacterial genomic DNA. An experiment was performed to examine the effect of standard autoclaving on the integrity of bacterial DNA, employing polymerase chain reaction (PCR) as an indicator of DNA integrity. Amplifiable PCR signal was observed at t = 10, 20 and 30 min autoclaving time for Pseudomonas aeruginosa NCTC 10662; at t = 10, 20, 30 and 40 min for Salmonella Nottingham NCTC 7832; and at t = 10 and 20 min for Escherichia coli NCTC 9001. Careful consideration should therefore be given to residual molecular artefacts in future risk and environmental impact assessments, where the legacy of residual genomic DNA from dead bacterial and higher organisms may act as a potential reservoir, thereby feeding horizontal gene transfer scenarios in viable cells with potential hazardous genes of virulence, persistence or antibiotic resistance characteristics.