Safe Disposal of Diphtheria Toxin

Like any dangerous toxin or chemical, diphtheria toxin should always be disposed of properly.

Diphtheria is a dangerous bacterial infection that ravaged Europe and America during a series of epidemics beginning in the 18th century. Following the development of a safe and reliable vaccine in 1924, it has been nearly eradicated in developed countries. The bacteria's secret weapon is a protein it secretes called diphtheria toxin (DT). It is essential to take the appropriate precautions to avoid possible harm to yourself or others when handling or disposing of this toxin in the lab.

Significance

DT is a protein and not a live agent; in this sense, the dangers posed by DT are more akin to those from a chemical agent than a live bacteria. According to the List Biological Labs MSDS, DT has no effect if taken orally, but it is extremely hazardous if injected even in minute doses. Pricking your skin with needles or other objects contaminated with DT is potentially dangerous, as is inhaling the toxin; for this reason it is recommended to avoid working with DT in the dried state. The University of Florida Environmental Health and Safety biosafety office lists the LD50 value (the dose estimated to kill 50 percent of those who take it) for DT as 0.1 micrograms per kilogram of body weight.

Prevention/Solution

Label and store DT in airtight containers in areas inaccessable to unauthorized personnel. Ensure adequate ventilation while working with DT; disposable items like gloves or absorbent pads that become contaminated with DT during the course of an experiment should be placed in plastic bags and deposited in appropriately labeled chemical waste containers. Always wear gloves, avoid direct contact with the toxin if possible and wash any areas of the skin that do come in contact with DT thoroughly.

Autoclaving

There are two preferred methods of sterilization that will inactivate DT. The first is known as autoclaving. An autoclave is a device that subjects equipment to hot high pressure steam. To safely dispose of waste toxin, loosen the cap on the container with the toxin so that the steam can enter, place it in a disposable container and place this in turn in an autoclave bag. Put the container inside the machine and autoclave it at 250 degrees Fahrenheit (121 degrees Celsius) for an hour; afterward, deposit the bag in a chemical waste container for destruction.

Sodium Hypochlorite/Hydroxide

Sodium hypochlorite (bleach) or sodium hydroxide will also denature and inactivate DT. Place the container with the toxin in a rack atop absorbent paper, then add a volume of sodium hypochlorite or sodium hydroxide equal to the volume of the DT solution to the container. Allow the mixture to sit for at least an hour, then securely seal the container, bag it and dispose of it in accordance with your lab or facility's guidelines.

Warning

Dry heat is not a safe method to inactivate DT; autoclaving or sodium hypochlorite are preferable. Different labs may have specific guidelines for working with hazardous toxins. Follow your lab's guidelines for disposal and know the location of chemical waste repositories. Always take care to transport, store and handle DT safely.

References

• University of Florida Environmental Health and Safety: Toxins of Biological Origin
• List Biological Laboratories: Diphtheria Toxin
• University of Washington Environmental Health & Safety: Toxins of Biological Origin
• University of Virginia Biosafety: Toxins