6568 Afr. J. Microbiol. Res.
Table 2. List of neutralizers tested.
Neutralizer Composition
A- 1% Physiological peptone water
Peptone 10.0 g
Sodium chloride 5.0 g
Disodium phosphate 3.5 g
Monopotassium phosphate 1.5 g
0.9% Saline 1000 ml
B- 0.6 % Sodium thiosulphate in 1% physiological peptone water C- Phosphate buffer saline
D- 0.1% Tween 80 in 1% physiological peptone water.
E- Dey-Engley broth
Sodium thioglycolate 1 g/L
Sodium thiosulfate 6 g/L
Sodium bisulfite 2.5 g/L
Polysorbate 80 5 g/L
Lecithin (soybean) 7 g/L
Tryptone 5 g/L
Yeast extract 2.5 g/L
Glucose 10 g/L
Distilled water 1000 ml
Table 3. Efficacy and toxicity of used neutralizers for disinfectants and antiseptics on S. aureus ATCC 6538 (Index microorganism for Gram-positive bacteria).
S/No. Chemical agent name Neutralizer
Efficacy Toxicity
Neutralizer exposed population (CFU)
Neutralizer with biocide (CFU)
Neutralizer efficiency ratio
Neutralizer exposed population (CFU)
Viability population (CFU)
Recovery percentage ratio
1 Sanigel 1% Physiological peptone 108 100 0.93 108 97 0.90
2 Hospidermin 1% Physiological peptone 104 96 0.92 104 88 0.85
3 Alcohol 1% Physiological peptone 107 97 0.91 107 99 0.93
4 AHD 2000 1% Physiological peptone 106 100 0.94 106 98 0.92
5 Sanipine 1% Physiological peptone 104 99 0.95 104 100 0.96
6 Sanismell 1% Physiological peptone 103 98 0.95 103 100 0.97
7 Lysoformin 3000 Dey-Engley 108 100 0.93 108 96 0.89
8 Chlorax 0.6% Na2S2O3 105 100 0.95 105 94 0.90
Sheraba et al. 6569
Table 3. Contd.
9 Trichlorol 0.6% Na2S2O3 103 99 0.96 103 93 0.90
10 H2O2 25% PBS 108 89 0.82 108 96 0.89
Table 4. Efficacy and toxicity of used neutralizers for disinfectants and antiseptics on P. aeruginosa ATCC 9027 (Index microorganism for Gram-negative bacteria).
S/No. Chemical agent name Neutralizer
Efficacy Toxicity
Neutralizer exposed population (CFU)
Neutralizer with biocide (CFU)
Neutralizer efficiency ratio
Neutralizer exposed population (CFU)
Viability population (CFU)
Recovery Percentage ratio
1 Sanigel 1% Physiological peptone 108 99 0.92 108 113 1.05
2 Hospidermin 1% Physiological peptone 105 96 0.91 105 113 1.08
3 Alcohol 1% Physiological peptone 107 100 0.93 107 113 1.06
4 AHD 2000 1% Physiological peptone 108 99 0.92 108 113 1.05
5 Sanipine 1% Physiological peptone 103 96 0.93 103 113 1.1
6 Sanismell 1% Physiological peptone 102 88 0.86 102 113 1.11
7 Lysoformin 3000 Dey-Engley 103 92 0.89 103 118 1.15
8 Chlorax 0.6% Na2S2O3 105 100 0.95 105 118 1.12
9 Trichlorol 0.6% Na2S2O3 102 97 0.95 102 118 1.16
10 H2O2 25% PBS 105 98 0.93 105 118 1.12
Table 5. Efficacy and toxicity of used neutralizers for disinfectants and antiseptics on A. niger ATCC 16404 (Index microorganism for fungi).
S/No. Chemical agent name Neutralizer
Eficacy Toxicity
Neutralizer exposed population (CFU)
Neutralizer with biocide (CFU)
Neutralizer efficiency ratio
Neutralizer exposed population (CFU)
Viability population (CFU)
Recovery percentage ratio
1 Sanigel 1% Physiological peptone 108 96 0.89 108 113 1.05
2 Hospidermin 1% Physiological peptone 108 97 0.90 108 113 1.05
3 Alcohol 1% Physiological peptone 108 93 0.86 108 113 1.05
4 AHD 2000 1% Physiological peptone 108 92 0.85 108 113 1.05
5 Sanipine 1% Physiological peptone 108 95 0.88 108 113 1.05
6 Sanismell 1% Physiological peptone 108 91 0.84 108 113 1.05
7 Lysoformin 3000 Dey-Engley 106 93 0.88 106 113 1.07
8 Chlorax 0.6% Na2S2O3 107 94 0.88 107 113 1.06
9 Trichlorol 0.6% Na2S2O3 107 97 0.91 107 113 1.06
10 H2O2 25% PBS 109 98 0.90 109 113 1.04
6570 Afr. J. Microbiol. Res.
Table 6. Efficacy and toxicity of used neutralizers for disinfectants and antiseptics on B. subtilis ATCC 6633 (Index microorganism for spores).
S/No. Chemical
agent name Neutralizer
Efficacy Toxicity
Neutralizer exposed population (CFU)
Neutralizer with biocide (CFU)
Neutralizer efficiency ratio
Neutralizer exposed population (CFU)
Viability population (CFU)
Recovery Percentage ratio
1 Sanigel 1% Physiological peptone 104 97 0.93 104 98 0.94
2 Hospidermin 1% Physiological peptone 104 98 0.94 104 92 0.88
3 Alcohol 1% Physiological peptone 104 95 0.91 104 94 0.90
4 AHD 2000 1% Physiological peptone 104 96 0.92 104 96 0.92
5 Sanipine 0.1% Tween in 1% physiological peptone 105 92 0.88 105 97 0.92
6 Sanismell 0.1% Tween in 1% physiological peptone 105 97 0.92 105 98 0.93
7 Lysoformin 3000 Dey-Engley 107 96 0.90 107 99 0.93
8 Chlorax 0.6% Na2S2O3 108 94 0.87 108 100 0.93
9 Trichlorol 0.6% Na2S2O3 106 92 0.87 106 100 0.94
10 H2O2 25% PBS 103 98 0.95 103 96 0.93
Table 7. Efficacy and toxicity of used neutralizers for disinfectants and antiseptics on S. hominis (Index microorganism for environmental isolate program).
S/No. Chemical agent
name Neutralizer
Efficacy Toxicity
Neutralizer exposed population (CFU)
Neutralizer with biocide (CFU)
Neutralizer efficiency ratio
Neutralizer exposed population (CFU)
Viability population (CFU)
Recovery percentage ratio
1 Sanigel 1% Physiological peptone 105 98 0.93 105 118 1.12
2 Hospidermin 1% Physiological peptone 104 95 0.91 104 94 0.90
3 Alcohol 1% Physiological peptone 106 92 0.88 106 100 94
4 AHD 2000 1% Physiological peptone 109 98 0.90 109 113 1.04
5 Sanipine 1% Physiological peptone 105 100 0.95 105 118 1.12
6 Sanismell 1% Physiological peptone 106 93 0.88 106 113 1.07
7 Lysoformin 3000 Dey-Engley 107 94 0.88 107 113 1.06
8 Chlorax 0.6% Na2S2O3 105 100 0.95 105 118 1.12
9 Trichlorol 0.6% Na2S2O3 102 97 0.95 102 118 1.16
10 H2O2 25% PBS 104 98 0.94 104 92 88
most difficult disinfectant to be neutralized and was neutralized with Dey-Engley broth against each test bacterium. This finding agrees with (Sutton et al., 1991; Buck and Rosenthal, 1996) who reported that Dey-Engley broth was an effective medium for neutralization of all
disinfectant solutions with the exception of 3%
hydrogen peroxide. Dilution in PBS containing 0.2% sodium thiosulphate (wt/vol) was found to be an effective neutralizer to hydrogen peroxide; this finding agrees with (Elkins et al., 1999) who reported that PBS containing 0.2% sodium
thiosulphate (wt/vol) was used to neutralize hydrogen peroxide against catalase found in P.
aeruginosa biofilm. Conversely, Sutton et al.
(1991), Holton et al. (1995) and Coates (1996) found that 5% thiosulphate and 0.025% catalase were effective for neutralization of hydrogen
peroxide. 0.5% sodium thiosulphate was observed to be effective neutralizer for chlorox and trichlorol against all challenge organisms except P. aeruginosa and B.
physiological peptone was the most effective neutralizer for alcohol, Hospidermin, AHD 2000 and Sanigel (alcohol-based gel) against all test bacteria, nearly similar to results reported by Traore et al. (2002) who stated that dilution with buffered saline was used because of its known effectiveness as a neutralizer for alcohol based hand-wash agents, on the other hand, Adams et al.
(2005) reported that mixture of 0.2% Tween 80, 1.17%
Lecithin, 0.1% Triton and 0.5% sodium thiosulphate in distilled water was effective neutralizer for alcohol based gel.
This study showed that dilution with 1% physiological peptone was the most effective neutralizer for Sanipane and Sanismel against each test bacterium except B.
subtilis, where in that case it was observed that 0.1%
Tween 80 in 1% physiological peptone is the most efficient neutralizer, this might be in contrast to Mohamed (2004) who found Letheen broth to be an effective neutralizer for QAC.
Conclusion
Evaluation of NE and toxicity should be performed prior to testing of a new biocide. We have determined the most effective neutralizers for the most common disinfectants and antiseptics used in the main vaccine production facility in Cairo, Egypt as a part in an environmental monitoring program. Based on our findings, 1%
physiological peptone water, 0.1% Tween 80 in 1%
physiological peptone, 0.6% sodium thiosulphate and Dey-Engley were the most effective. The efficacy of neutralizers should be determined using several index test organisms and environmental isolates if detected.
ACKNOWLEDGEMENTS
The authors would like to thank Dr. Hamdalla Hafez Zedan, chairman of the Egyptian Company for Production of Vaccines, Sera and Drugs (EGYVAC) for his continuous support and help in carrying out the study, Dr.
Mohamed Rabei, Chairman of the Holding Company for Production of Vaccines, Sera and Drugs (VACSERA) for his continuous encouragement and Dr. Ramy Karam
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