of 4 1 were prepared with phosphate buffer to an approximate concentration of 2 0 u00d7 10 7 organisms ml immediately following the fourteen 14 day plating all samples except the positive control were rechallenged with 0 1 ml of the appropriate challenge organism an additional positive control was prepared to verify the concentration and monitor the growth of the rechallenge inoculum for the remainder of the twenty eight 28 day test period within fifteen 15 minutes of the addition of the rechallenge and at twenty one 21 and twenty eight 28 days exposure samples were taken diluted and plated as in 3 3 a neutralizer efficacy screen was completed for each exposure time and consisted of a one ml of uninoculated test solution being aseptically added to a 9 0 ml deb blank and thoroughly mixed duplicate 1 ml aliquots from the broth were transferred to petri plates and one ml of a bacillus subtilis spore suspension containing approximately 100 cells ml was added all plates were poured using dey engley agar the plates were incubated at 32 u00b0 35 u00b0 c for 48 72 hours tables 16 20 each table showing the cfu colony forming units of organism in the test solution and positive controls at each time point neutralizer efficacy results found in table 21 the concentrations of s aureus p aeruginosa and e coli were reduced to at least 0 1 three log values of the initial.