The killing activity of microwaves on some non-sporogenic and sporogenic medically important bacterial strains.

The killing activity of microwaves of 2450 MHz frequency and 325 W, 650 W and 1400 W power on some bacterial strains was investigated. Vegetative strains of Staphylococcus aureus, Streptococcus pyogenes Group A, Escherichia coli, Pseudomonas aeruginosa and Enterococcus faecalis and spores of Bacillus subtilis and Bacillis stearothermophilus in aqueous suspensions were exposed to 325 W and 650 W waves for different lengths of time. Enterococcus faecalis and spores of B. subtilis and B. stearothermophilus were exposed additionally to 1400 W waves in aqueous and 'dried' suspensions. Vegetative bacteria were promptly killed in 5 min or less, E. faecalis being slightly more resistant. Bacterial spores were only killed in aqueous suspension when a 1400 W setting was used for 10 to 20 min. Bacterial spores adhering to the tube walls after the aqueous suspension was poured out were reduced in number. We assume that the conventional microwave ovens available on the market may be used for a high level of disinfection but not for sterilization, and only then if sufficient water is present.