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Volume 9, Number 6—June 2003
Synopsis

Inactivation of Bacillus anthracis Spores

Ellen A. Spotts Whitney*, Mark E. Beatty*, Thomas H. Taylor*, Robbin Weyant*, Jeremy Sobel*, Matthew J. Arduino*, and David A. Ashford*Comments to Author 
Author affiliations: *Centers for Disease Control and Prevention, Atlanta, Georgia, USA

Main Article

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)
 1250 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
1000 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 μWs/cm2
 0.1 mL of 108 B. anthracis spore suspension dried on aluminum carriers
 <96h
 2.4 log reduction, unreliable results
 30
450,000 μWs/cm2
 0.1 mL of 108 B. anthracis spore suspension dried on ceramic carriers
 <96h
 2.03 log reduction, unreliable results
52.8 x 106 μWs/cm2
 0.1 mL of 108 B. anthracis spore suspension dried on wood carriers
 30h
 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.

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Page created: December 21, 2010
Page updated: December 21, 2010
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