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 Nis 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


25% Fetal Calf Serum

 

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 % H₂O

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

  1. * More active at elevated Temperature

 

  1. The B. subtilis endospore would best serve as the surrogate biological indicator in an anthrax germ warfare screening program being the most resistant species.

 

  1. Studies with a potential viral germ warfare organism (Small pox as Vaccinia surrogate) showed the value of the D-10 quantal determination as follows in assessing the strength of household remedies.

     Agent                                     D-value

                                                   3 % H2O2                                        5 seconds
                                                   EPA Quat                                       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

 

 

 

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