Evaluation mL sample to a tube containing 8

Evaluation of disinfectants is often based on laboratory suspension tests according to PrEN1276 19. 1 mL of a bacterial test suspension adjusted to 1.5 x108 to 5.0×108 cfu/mL using McFarland standard and was added to 1 mL interfering substance. (5% yeast extract). The mixture was maintained at 20°C+1°C for 2 min +10 s. Then 8 mL of the product test solution were added and the mixture was maintained at 20°C+1°C for 1, and 5 min exposure time. At the end of the contact times an aliquot was taken and the bactericidal activity in this portion was immediately neutralized or suppressed by dilution-neutralization method adding 1 mL sample to a tube containing 8 mL of specific neutralizer dissolved in Tryptone Soya Broth 30.0 g/L and 1 mL water mixed by vortexing, and left at 20oC. After 5 min neutralization time, duplicate 1.0ml volumes were pour plated with tryptone soya agar and incubated at 37oC for 48 hr prior to counting. The microbicidal effect (ME) was calculated by subtracting the log of viable count after disinfection (Na) from the log of the initial count in the bacterial test suspension (N x 10-1). The products must achieve a five log reduction in viable counts (ME value of 5 or higher) to accept as a microbicidal compound.3.2 Surface test: The surface test based on the surface test method described in PrEN 13697 20 which specifies a quantitative surface test for the evaluation of bactericidal activity of chemical disinfectants used in the food industry ,stainless steel Coupons measuring 1.5 x 2 cm were autoclaved at 121°C for 15 min, To prepare the test suspension two minutes prior to the actual test 1 mL of the bacterial test suspension containing 1.5 x109 to 5.0×109 cfu/mL was added to 1 mL of the interfering substance(yeast extract 5%) and mixed. The test surfaces were placed in an open Petri dish ensuring that the stainless steel coupons were in horizontal position. Then they were inoculated with 0.05 mL of the test suspension and interfering substance mixture and dried in an incubator at 37°C for 45-55 min until they were visibly dry. After drying the temperature of the surface was adjusted to room temperature. Then the inoculum was covered with 0.1 mL of the product test solution, or for the water control with water of standardized hardness instead of the product. After the chosen exposure times of 5 min the surfaces were transferred into separate flasks containing 10 mL of an appropriate neutralizer and glass beads. After a neutralization time of 5 min a series of tenfold dilution were prepared in Tryptone-NaCl solution. The number of surviving test organisms was determined quantitatively. For each test organism, product test concentration and exposure time, the reduction in viability in comparison to the water control was calculated.IV. Results And DiscussionTable (5) Staphylococcus log reduction on suspension test after one minute:DYNE-O- MIGHT 1%ZIXVIROX 0.5%.POLYCARP 3%VIRKON S 1%S. INTERMEDIUS