Various factors that affect the antibacterial effect of a product processed with an inorganic silver antibacterial

We conducted a test on pieces of polypropylene to which an inorganic silver antibacterial agent had been added, to find the antibacterial effect, following the JIS Z 2801 antibacterial test method. We used the method of changing the nourishment concentration (1/5 - 1/500NB), the initial number of bacteria (10E3-10E8 CFU/ml), and the culturing temperature (25degC, 35degC), and then inspected what kind of influence those factors had on the number of surviving Staphylococcus aureus and Escherichia coli. The antibacterial activity (R) value of the test pieces 1 and 2 was R = 0.6, R = 0.8 against S. aureus and that of test pieces 3 and 4 was R = 6.0 against E. coli. S. aureus did not multiply in the low nourishment concentration. On the other hand, E. coli, despite its high sensitivity to Agsup(+) multiplied in the high nourishment concentration and was unaffected by temperature. Because of the rapid increase in E. coli, it was thought that the number of the surviving E. coli had a certain relation to the multiplying speed on the test piece surface or at a remote position. From comparisons of the TOC (Total Organic Carbon) concentration that is the dirt to nourishment concentration index, it was also thought that it was hard for dirt to stick onto the antibacterial processed product. Taking into consideration that the antibacterial processed product would be used in the ordinary living environment, we compiled the test results at 25degC. As for S. aureus, when its initial number was less than 10E5 CFU/ml, it decreased to 1/10 - 1/100 in relation to the antimicrobial-activity value (R value) of the test piece. On the other hand, E. coli multiplied remarkably where the nourishment concentration was high, even if the R value was large. In these tests, we found that the antibacterial effective area against E. coli was small. We must check the antibacterial effective area before we start planning an antibacterial processed product.