Table
2. Efficiency of chemicals, gases, and radiation on the inactivation
of Bacillus sporesa |
|
Method |
Concentration
|
Inoculum size
|
Time
|
Efficiency
|
Ref.
|
|
Chemical sterilization
|
Calcium hypochlorite
|
20 ppm available; Cl2,
pH 8.0, 20ºC
|
3 x 105–4 x 105
spores of Bacillus subtilis in 5.0 mL sterile distilled H2O
|
4.8 min
|
99% killed
|
8
|
25 ppm available; Cl2,
pH 6.0, 20ºC
|
2 x 107 spores/mL of B.
metiens in 10 mL of sterile distilled H2O
|
2.5 min
|
0.061 (log of average % survivors)
99% killed
|
9
|
Free available chlorine
|
2.4–2.3 mg/L available; CL2,
pH 7.2, 22ºC
|
1.1 x 105 spore suspension
of B. anthracis
|
1 h
|
>99.99% killed (1 spore/mL survived)
|
10
|
Sodium hypochlorite (NaOCl)
|
0.05%, pH 7.0, 20°C
|
Spore suspension of B. subtilis
globigii, representing 1.6–2.2 x 109 CFU/mL
|
30 min
|
99.99% killed
|
11
|
0.05%, pH 11.0, 20°C
|
50% spores survived
|
Hydrogen peroxide (H2O2)
|
25.8%, 24°C
|
B. subtilis globigii spore
suspension
(no concentration)
|
15 min
|
0.001% survived
|
12
|
25.8%, 76°C
|
<1 min
|
<0.0001% survived
|
0.88 mol/L, pH 5.0
|
106 CFU/mL B. subtilis
spore suspension
|
3 h
|
100% killed
|
13
|
0.88 mol/L, pH 4.3
|
10 mL B. subtilis spore suspension
coated onto stainless steel carriers
|
6 h
|
100% killed
|
Peracetic acid (CH3COOOH)
|
0.13 mol/L, pH 5.0, 6.5, 8.0
|
106 CFU/mL B. subtilis
|
<30 min
|
100% killed
|
13
|
0.39 mol/L, pH 4.0, 7.0, 9.0
|
10 mL B. subtilis spore suspension
coated on stainless steel carriers
|
24 h
|
100% killed
|
Formaldehyde (CH2O)
|
4% in water
|
108/mL B. anthracis
|
2 h
|
104 inactivation factor
|
14
|
400 mg/m3, 30% RH
|
102–3 x 108
B. globigii NCTC 10073 dried on disks
|
22 min
|
1 log10 reduction, at
23.5°C–25°C
|
15
|
280 mg/m3, 50%RH
|
31 min
|
250 mg/m3, 80% RH
|
16 min
|
400 mg/m3, 98% RH
|
9 min
|
Glutaraldehyde (C5H8O2)
|
2% in water, pH 8.0
|
108/mL spores B.
anthracis
|
15 min
|
104 inactivation factor
|
14
|
Sodium hydroxide (NaOH)
|
5%, 27.8ºC
|
7 x 109 spores/mL B.
subtilis
|
1.5 h
|
99% killed
|
16
|
5%, 21.1ºC
|
3.6 h
|
99% killed
|
Gaseous sterilization
|
Ethylene oxide (C2H4O)
|
Exposed to constant boiling HCL at
20°C for 30 min before exposure to ethylene oxide at room temperature
|
B. globigii and B. anthracis
dried onto suture loop carriers (no concentration)
|
1 h
|
100% killed
|
17
|
500 mg/L, 30%–50% RH, 54.4°C
|
~106 spores B. globigii
on nonhygroscopic surfaces
|
30 min
|
4-log reduction
|
18
|
~106 spores B. globigii
on hygroscopic surfaces
|
6-log reduction
|
Chlorine dioxide (ClO2)
|
40 mg/L, 60%–80% RH, 25°C–27ºC
|
1.4 x 106/0.2 mL B.
subtilis subsp. Niger dried on paper and aluminum foil
strips
|
1 h
|
100% killed
|
19
|
30 mg/L, 80%–85% RH, 30ºC
|
106 spores/biologic indicator;
B. subtilis subsp. Niger
|
30 min
|
100% killed (estimated time to kill
90%, 4.4 min)
|
20
|
6–7 mg/L, 20%–40% RH, 23ºC
|
106 spores/biologic indicator;
B. subtilis subsp. Niger
|
30 min
|
101 CFU/biologic indicator
(estimated time to kill 90%, 4.2 min)
|
21
|
70%–75% RH for 0.5 before exposure,
23ºC
|
15 min
|
0 CFU/biologic indicator (estimated
time to kill 90%, 1.6 min)
|
Hydrogen peroxide (H2O2) plasma
|
0.208 mg/L, 1.5 Torr pretreatment
for 10 min; 2.49 MHz, 150 W of pulsed plasma in a cycle of 0.5 ms
plasma on, 1.0 ms plasma off
|
3.4 x 105 B. subtilis
subsp. globgii spores on paper disks and packaged in spun-bonded
polyethylene
|
15 min
|
100% killed
|
22
|
Methylene bromide (CH3Br)
|
3.4–3.9 g/L, room temperature in
the presence of moisture
|
1 x 105–5 x 107
spores of B. anthracis dried on sterile filter paper strips
|
24 h
|
100% killed
|
23
|
Peracetic acid vapor (CH3COOOH)
|
1 mg/L, 80% RH
|
6 x 105 – 8x 105
B. subtilis niger dried on filter-paper disks and
glass squares
|
10 min
|
<1 spore remained on paper and
glass
|
24
|
1 mg/L, 60% RH
|
2 spores remained on paper; 38 spores
remained on glass
|
1 mg/L, 40% RH
|
24 spores remained on paper; 1,530
spores remained on glass
|
Propylene oxide (C3H6O)
|
1,250 mg/L, 86% RH, 36°C–38ºC
|
9.5 x 105–1.1 x 106
spores B. subtilis niger dried on filter paper
|
1.05 h
|
90% killed
|
25
|
1,000 mg/L, 37°C
|
2.5 x 107 spores B.
subtilis niger in cereal flakes
|
3 h
|
3.7% survived
|
Ozone (O3)
|
1.0 mg/L generated in water pH 3
|
1.8 x 105 spores/mL B.
cerus
|
5 min
|
<101 CFU/mL survived
|
26
|
3.0 mg/L, preconditioned at 54% RH
|
108–2 x 108
B. subtilis dried on filter paper
|
1.5 h 95% RH
|
<0.001% survived
|
27
|
108–2 x 108
B. cerus dried on filter paper
|
1.5 h 95% RH
|
<0.001% survived
|
900 ppm, preconditioned at 65%–70%
RH for 15 h
|
5 x 107 spores/glass coupon
|
30 min 80% RH
|
100 survived
|
28
|
60 min 70% RH
|
100 survived
|
Radiation
|
UV
|
85% 2537A
|
B. anthracis (mixed spores
and vegetative forms) in beef extract agar pH 7.4 (no concentration)
|
452 ergs/mm2
|
90% killed
|
29
|
4,800 mWs/cm2
|
0.1 mL of 108 B. anthracis
spore suspension dried on aluminum carriers
|
<96 h
|
2.4 log reduction, unreliable results
|
30
|
450,000 mWs/cm2
|
0.1 mL of 108 B. anthracis
spore suspension dried on ceramic carriers
|
<96 h
|
2.03 log reduction, unreliable results
|
52.8 x 106 mWs/cm2
|
0.1 mL of 108 B. anthracis
spore suspension dried on wood carriers
|
30 h
|
0.67 log reduction
|
Gamma irradiation
|
|
106 spores/mL B. anthracis
|
Dose of 1 x 106 rad
|
100% killed
|
31
|
|
aRH,
relative humidity; conversions: 1 ppm = 1 mg/L; mol/L = gram molecular
weight/L; 1 rad = 100 ergs/g; and 1 watt = 107 ergs/s. |