The hygiene levels in home laundry operations in Japan have been changing with the changes in lifestyle. Microbial transmission through home laundry has been reported, but mainly in North American and European countries. The home laundering situation in Japan is unique among many countries, and the most characteristic point is that Japanese use the leftover bath water for laundering the next day. However, such a unique custom may cause household microbial transmission. In order to clarify the link between the microbial transmission and the home laundering operation in Japan, a bacteriological investigation of various articles was done. Children's underpants, bath towels, kitchen rags, the washing machine itself and the leftover bath water were investigated. Although variations in bacterial strains were seen, many Staphylococcus spp. were isolated from every sample. Although pathogenic strains were not detected, some opportunistic pathogens were detected. Furthermore, since many bacteria were isolated from bath water, home laundering operations with the used bath water may cause microbial contamination of the laundry.
The effects of food additives on the inactivation of spores of Bacillus subtilis, Bacillus coagulans and Bacillus stearothermophilus by reciprocal pressurization (six reciprocal 5-min pressurization cycles) and continuous pressurization (30-min pressurization) were investigated at 400MPa. As food additives, glucose (12%, w/v), sodium chloride (6%, w/v) and ethanol (20%, w/v) were selected. RP treatment increased the inactivation ratio of three strains. Addition of food additives decreased the inactivation ratio in continuous pressurization and reciprocal pressurization treatment except in the case of the addition of sodium chloride in reciprocal pressurization treatment.
The antimicrobial activity of chitosan with different molecular weights (MWs) and different degrees of acetylation (DA) was examined to clarify how the activity depends upon the molecular structures. We determined minimum growth inhibitory concentrations (MICs) of various types of chitosan in L broth or its modified medium against bacteria and yeasts. The MICs against Gram-positive bacteria were relatively low for chitosan preparations with higher MWs and that against Gram-negative bacteria were at their minimum at around a MW of 11, 000 to 30, 000. An increase in the DA of the amino group in the chitosan molecule caused less activity. The antimicrobial activity varied with the genus as well as species of bacteria and yeasts. For application of chitosan as a preservative to food, pharmaceuticals, and other materials, the data obtained here on the characteristics and antimicrobial spectrum may be useful.
Effects of the amounts of dirty materials and the numbers of microorganisms adhering to antimicrobial socks treated with modified metal ions (Cu2+ or Zn2+) were investigated. Correlation coefficient values between the dirty materials (ammonium nitrogen, Cl-, KMnO4 consuming substances, and total organic materials) and the bacterial numbers on control socks were respectively 0.898, 0.892, 0.939, and 0.921, suggesting a high correlation. In the meantime, those of antimicrobial socks were 0.572, 0.680, 0.491 and 0.559, respectively. Low values were also found in the fungal numbers. These results suggest that the antimicrobial socks treated with metal salts would contribute to decreasing the bacterial numbers adhering to them.
The adaptation of bacteria to mono-and bis-type quaternary ammonium compounds (QACs) was carried out and studied. The minimum inhibitory concentration (MIC) of bis-QACs against the bacteria in contact with bis-QACs was nearly the same as that against the control. However, the MIC of mono-QAC against the strains adapted to mono-QAC was higher than that against the control. Moreover, bis-QACs were effective against even the strains adapted to mono-QAC. As the cell surface of the strains adapted to mono-QAC changed to hydrophilic, the difference in the bacterial adaptation was thought to arise from a potent property of bis-QACs whose antimicrobial characteristics are independent of the change in the cell surface hydrophobicity.