The D-10 quantal value describes the ability of a chemical or physical agent to reduce an exposed Microbial population 90% (one log10) under standard conditions of Time, Temperature, Concentration or Dose. It is widely used in infection and contamination control in pharmaceuticals, medical devices, tissue and biotech. It is my purpose here to conveniently compile D value data from our laboratory and from the literature. In doing so we quickly see how some organisms are relatively easy to destroy and some are much more difficult. We also note that different technologies are used against different organisms in order to control the given population. Specifically, we will report on D values obtained by sterilization with gamma irradiation, by chemical germicides and by antibiotics.
The D value is calculated in several ways all of which compare the surviving population to the initial population either (a) mathematically by some variation of the Karber-Spearman or Stumbo equation or (b) by graphic analysis of the slope of dose-survival curves.
Mathematically,
Where N 0 is the initial population before and N1 is the population after exposure as log10
D Values Obtained by Gamma Irradiation
(1) Drug and device research require this calculation for IRRADIATION sterilization and for measurement of the resistance of Biological Indicators (2). FOOD Microbiologists require this calculation for determination for the proper conditions to eradicate pathogens from the food supply. SEE TABLE I for a list of microorganisms as referenced in the literature for these two applications. Note the effect of temperature and chemical menstruum of the suspending material. One also notes the marked difference in resistance between bacterial spores and vegetative organisms and the effect of temperature in increasing the D-Value. One also notes the lower resistance of bacterial Table 1 as compared to viruses Tables 2a and 2b.
CHEMICAL GERMICIDES and ANTIBIOTICS
D Values Obtained by Chemical Agents
D-10 studies can be used to rank the relative potency of chemical germicides such as disinfectants (environmental surfaces, reprocessing protocols), antiseptics (hand hygiene claims) and topical antibiotics (otic, ophthalmic and respiratory claims) for either product development or public health findings.
SEE TABLE 3 for some results from GIBRALTAR research on the effects of Chlorine Phenolics, Quats, peroxide, alcohol, alkali, and iodine including biohazard agents such as Anthrax and Smallpox surrogates.)
Table 1: Irradiation D Value | |||
Vegetative Organisms | Classification | kGy | Reference |
Listeria monocytogenes | A | 0.62 | 1 |
Salmonella sp. | B | 0.6 | 2 |
E. coli O157:H7 | B | 0.3 | 2 |
Yersinia enterocolitica | B | 0.2 | 2 |
Campylobacter sp. | B | < 0.2 | 2 |
Staphylococcus aureus | B | 0.5 | 2 |
Brucella abortus | A/B | 0.15 | 2 |
Salmonella muenster | A | 0.6 | 3 |
Mycobacterium fortuitum | A | 0.6 | 3 |
Clostridium difficile | A | 0.9 | 3 |
Aspergillus fumigatus | A | 0.6 | 3 |
Candida albicans | A | 0.9 | 3 |
Streptococcus faecalis | A | 1.56 | 3 |
Salmonella typhimurium | C | 0.2 to 1.3 | 4 |
Pseudomonas spp. | C | 0.06 | 4 |
Staphylococcus aureus | C | 0.2 | 4 |
Streptococcus faecium | C | 2.8 (dry) | 4 |
Micrococcus radiodurans | C | 2.2 | 4 |
Lactobacillus brevis | C | 1.2 | 4 |
Acinetobacter radioresistens | C | 1.3-2.2 | 4 |
Aspergillus niger | C | 0.5 | 4 |
Saccharomyces cerevisiae | C | 0.5 | 4 |
Anaerobic Spore Formers |
| ||
Clostridium botulinum | C | 1.4 to 4.2 | 4 |
Clostridium sporogenes | C | 1.6 to 2.2 | 4 |
Clostridium tetani | C | 2.4 | 4 |
Aerobic Spore Formers | |||
Bacillus subtilis | C | 0.6 | 4 |
Bacillus pumilus E-601 | C | 1.7 | 4 |
Bacillus pumilus E-601 | C | 3.0 (dry) | 4 |
Bacillus pumilus ATCC 27142 | C | 1.4 to 1.8 | 4 |
Cryptococcus laurentiii | C | 3.1 | 5 |
Cryptococcus albidus | C | 2.7 | 5 |
| Cryptococcus uniguttilans | C | 1.4 | 5 |
Legend A = Sewage/Lab Waste B = Meat C Wet or Dry | |||
Table 2b: Effect of Gamma Irradiation on Viruses in Water or Serum | |||||
D-value kGy |
Reference | ||||
Virus |
Water |
|
100% Bovine Serum |
100% Frozen Serum | |
Picorna | 0.3 | 1.9 | 5.0 | N/A |
|
Reo | 0.35 | 3.0 | 8.0 | N/A |
|
Parvo | 0.4 | 4.5 | 10.7 | N/A |
|
Pox | 0.2 | 1.0 | N/A | N/A |
|
HSV | 0.17 | 0.4 | N/A | N/A |
|
SV40 | 3.9 | N/A | N/A | 26 |
|
Note: Viruses are protected from destruction by irradiation by serum. Resistance is directly proportional to serum concentration. Frozen serum is even more protective than non- frozen serum. | |||||
Table 2a: Effect of Gamma Irradiation on Viruses
| ||
Virus |
D-value kGy |
Reference |
Porcine Parvovirus | 4.0 |
|
Picomavirus Swine Vesicular Disease | 2.8 |
|
Adenovirus | 4.5 |
|
Avian Pox | 2.0 |
|
Newcastle Disease Virus | 2.0 |
|
Foot and Mouth | 13.0 |
|
Coxsackievirus | 4.5 |
|
Notes 1. As a general rule the smaller the virus the more resistant to irradiation and there is no resistance pattern as one compared RNA with DNA. 2. Also, one notes a greater degree of radioresistance for viruses as compared to B, Y and M (see Table 1). | ||
Table 3: Germicidal Strength Description Isaac Newton said that you don’t know about a thing unless you can give it a number- This has been useful in the earlier data as to providing meaningful data when measuring the RESISTANCE of specific organisms to ionizing radiation.
For chemical germicides the D-10 number features conversely the STRENGTH of a chemical agent as to its oxidizing or denaturing ability.
The following data were developed in our lab in studies designed to compare the strength of a variety of germicides against three spores of the genus Bacillus for purposes of comparative biology and for assessment of anthrax surrogate potential.
| |||
Germicide |
Spore of Bacillus spp. | ||
anthracis | cereus | subtilis | |
10% Bleach [Sodium hypochlorite] | 4 minutes | 4 minutes | 5 minutes |
3 % H₂O₂ | 1 minute | 5 minutes | 10 minutes |
NaOH 0.5N | 3 hours | 3 hours | 6 hours |
Citric Acid 1.5% * | > 6 hours | > 6 hours | > 6 hours |
EPA Quat (750ppm) | 1.5 hours | 2.5 hours | 6 hours |
Iodophor 10% PVPI | 10 minutes | 15 minutes | 15 minutes |
Phenolic Amyl Phenyl Phenol | > 6 hours | > 6 hours | > 6 hours |
70% IPA | > 6 hours | > 6 hours | > 6 hours |
Notes
Agent D-value 3 % H2O2 5 seconds 70% IPA 5 seconds 70% EtOH > 5 seconds
| |||
References
1. Rajkowski, K. 2008; Radiation D10-Values on Thawed and Frozen Fish – Listeria monocytogenes, J. Food Protection 71 (11): 2278-2282
2. Somers, C. 2004 et al; D-10 Value and Elimination of Food-Borne Pathogens, CIRMS Gaithersburg, MD, Abstract Eastern Regional Research Center
3. Garcia, M. et al 1987; Evaluation of Gamma Radiation Levels for Reducing Pathogenic Bacteria and Fungi in Animal Sewage and Laboratory Effluents. Canadian Journal of Veterinary Research 51: 285-289
4. Preset, R. et al; Clinical Diagnostic Lab of Immunology, Sweden. Google citation “D-10 Irradiation Values of Viruses”
5. Mureira, R.G. et al; Factors Affecting Radiation D-Value (D10) of an E. coli and Salmonella typhimurium Cocktail Inoculum in Fresh Produce. Journal of Food Science 77: 104-111.
6. Prince, D.L. et al 1999; Irradiation Studies of Cryptococcus Isolated from Devices. Medical Device and Diagnostic Industry News. Canon Publications
7. Thomas, F.C. et al 1981; Gamma Ray Inactivation of Some Animal Viruses. Canadian Journal of Comparative Medical Virology 45: 397-3999
8. Block, S.S. 2000; Disinfection, Sterilization and Preservation 5th Edition Lippincott Williams.
9 Sullivan et al. 1971 Inactivation of 30 Viruses by Gamma Irradiation Applied Microbiology p. 61-65
