Warming and Sterilizing Towels by Microwave Irradiation

Dielectric heating by microwave irradiation is well known to have an effect on killing microorganisms (Lund, 1975; Metaxas and Meredith, 1988). Microwave irradiation is used for the sterilization of food products (Chipley, 1980; Fung and Cunningham, 1980; Cross and Fung, 1982; Rosenberg and Bogl, 1987), and medical appliances and materials, such as acrylic resin dentures (Polyzois et al., 1982; Thomas and Webb, 1995), scalpel blades (Rosaspina et al., 1994a, 1994b), polyethylene catheters (Griffith et al., 1993) and plastic tissue culture vessels (Sanborn et al., 1982). The polar compounds in the materials, when exposed to microwave irradiation, generate heat by the collision and friction between molecules. Most microorganisms are killed by the heat generated. Thus, it is important that water is present in the irradiated materials. However, the possibility of nonthermal microwave effects has been proposed (Frolich, 1975; Cope, 1976; Pickard and Rosenbaum, 1978). In the aging society of Japan, it has become of increasing importance to care for aged persons or bedridden patients. One of the activities of caregivers is the wiping of patients’ bodies which requires sterile, comfortably warm towels. In this study, we sterilized towels by microwave irradiation. The opportunistic pathogens, S. aureus, P. aeruginosa and C. albicans, were seeded into the towels, which were then subjected to microwave irradiation. Then, bacteria were cultured in broth or on agar plates to confirm the survival rate. We compared the survival rate of bacteria contained in a small moist gauze with that of bacteria attached to a small dry gauze, following microwave irradiation. The degree of moistness of the towel is discussed.