Microwaves in the laboratory: effective decontamination.

OBJECTIVE: We hypothesize that microwave irradiation of certain contaminated materials typically used in a clinical laboratory or a home healthcare setting could produce efficient and effective sterilization when compared to standard autoclave methods.
DESIGN: A standard household carousel microwave oven unit used at the High setting was employed to expose certain materials that had been contaminated with either bacteria or yeast to microwaves for specific intervals of time. Following each time interval, materials were checked for effectiveness of decontamination using standard culture techniques and colony counting. Additionally, powdered media was prepared and microwave irradiated for specific times. The media was then poured into plates and checked for microbial contamination; another set of plates was examined to determine the ability of the irradiated media to support bacterial growth.
SETTING: This study was carried out at Texas Tech University Health Sciences Center in Lubbock TX. MAIN OUTCOME MEASURE: Standard culture and colony counting techniques were used to determine the efficacy of microwave sterilization.
RESULTS: The study indicated that microwave irradiation provided effective and efficient sterilization of all materials tested. Of the bacteria studied, only E. coli survived beyond 30 seconds of microwave exposure. Yeast did not survive beyond 15 seconds of microwave exposure. Swabs and gauze contaminated with bacteria or yeast were completely sterilized after 30 seconds. After three minutes in the microwave oven, powdered, prepared media was free of contamination while able to support growth when inoculated with S. aureus.
CONCLUSION: We conclude that a household carousel microwave oven unit can provide fast, effective sterilization of certain contaminated materials typically used in a clinical laboratory, student laboratory, or home healthcare setting.