Schick Introduces a Test for Diphtheria

Date 1913

Béla Schick developed a skin test for determining an individual’s susceptibility to diphtheria.

Locale University of Vienna, Austria

Key Figures

• Béla Schick (1877-1967), Hungarian microbiologist and pediatrician
• Edwin Klebs (1834-1913), German microbiologist
• Friedrich August Johannes Löffler (1852-1915), German microbiologist
• Pierre-Paul-Émile Roux (1853-1933), French microbiologist
• Alexandre Yersin (1863-1943), Swiss microbiologist
• Emil von Behring (1854-1917), German microbiologist

Summary of Event

Diphtheria is a serious disease of the upper respiratory tract—the mouth, nose, and pharynx. The person with this disease may have a fever, a sore throat, and pain all over the body. If the disease is not treated with antibiotics, the infection spreads and causes tissue damage in the heart or kidneys and the victim will eventually die.

Diphtheria is caused by Corynebacterium diphtheriae, a rod-shaped species of bacteria. The bacterium can be spread from one person to another by touching or by droplets (for example, from sneezes). Once it enters a person’s body, the bacterium releases protein toxins that destroy the membranes and inner structures of cells.

In the 1800’s, this disease was not yet understood, but the first steps toward that task were taken. Louis Pasteur, Robert Koch, and other microbiologists (scientists who study organisms too small to be seen by the naked eye) established the germ theory of disease, showing that infectious diseases are carried by microorganisms, usually bacteria or viruses. Diphtheria, typhoid fever, scarlet fever, tuberculosis, and several other diseases were major killers in the nineteenth century, especially among patients in hospitals. Microbiologists were determined to discover the microorganisms that caused these diseases.

In 1883, the German microbiologists Edwin Klebs and Friedrich August Johannes Löffler raised guinea pigs infected with diphtheria. Under microscopes, they observed rod-shaped bacteria growing in blood samples from the infected animals. When this bacterium was injected into healthy guinea pigs, they became ill with diphtheria, too. In this way, the scientists proved that this rod-shaped bacterium was the cause of diphtheria.

Löffler believed that these bacteria hurt their victims by releasing a toxin (a chemical that damages cells). In 1888, microbiologists Pierre-Paul-Émile Roux and Alexandre Yersin, working together at the Pasteur Institute in Paris, separated the diphtheria bacteria from the serum in which they were being grown. Roux and Yersin then injected the bacteria-free serum into healthy animals. The animals soon came down with diphtheria, even though they had not been exposed to the bacteria. The scientists realized that a toxin was being released by the Corynebacterium diphtheriae into the growth serum, and that it was this toxin that made people and animals ill.

Now microbiologists could go to work finding a vaccine and designing methods of diagnosing and treating diphtheria victims. In 1890, German microbiologistEmil von Behring discovered that the blood of animals infected with diphtheria produced an antitoxin, a chemical that binds to a toxin and makes it harmless. Behring realized that the antitoxin might be helpful in producing a vaccine to protect people against diphtheria. He injected animals with weakened diphtheria toxin—just enough so that their immune systems would create antitoxin but not enough to hurt the animals. Unfortunately, this diphtheria toxin was too dangerous to use on humans. Behring’s work, however, led to the later use of diphtheria antitoxin produced in horses as a treatment for human victims of the disease. In 1923, a formalin-treated toxin was used to vaccinate people against diphtheria and was found to be safe.

In 1908, Béla Schick, a pediatrician and microbiologist from Boglár, Hungary, became an assistant to Theodor Escherich at the University of Vienna, Austria. These two scientists began studying diseases caused by bacteria, including diphtheria and scarlet fever. In 1913, Schick used Behring’s work with antitoxins to develop a test that would show how susceptible a person was to catching diphtheria. The result was the Schick test, which proved to be simple and reliable. About 0.1 milliliter of a weakened toxin solution is injected just under the skin inside a patient’s arm. The toxin is treated so that it will lead to a bit of swelling in susceptible persons without hurting them. If the patient is susceptible to diphtheria, a reddened, swollen rash (caused by damaged skin cells) will appear around the injection site within a few days. A person who is not susceptible will have no reaction, because the toxin is not causing damage.

Those with positive results on the Schick test should be immunized. People who are already suffering from diphtheria can be treated with a combination of antibiotics and horse serum antitoxin. Antibiotics destroy the Corynebacterium diphtheriae bacteria, while the horse serum antitoxin destroys the diphtheria toxin until the victim’s body is strong enough to make enough of its own antitoxin.

Significance

Schick’s test for diphtheria became a valuable tool for identifying the disease and which people most needed immunization. As a result of his work, Schick was named Extraordinary Professor of Children’s Diseases at the University of Vienna in 1918. His test saved thousands of lives, especially among children, who tend to be susceptible to diphtheria. In the mid- to late 1920’s, when the first successful toxoid vaccine was available, the number of cases of diphtheria around the world dropped dramatically.

During the first two decades of the twentieth century, before the test and vaccine were available, the United States alone saw between 150,000 and 200,000 diphtheria cases every year. By the 1970’s, the number of diphtheria cases in the United States had dropped to roughly 10 per year.

The work of Schick and others also helped show how microorganisms are present everywhere in the environment and can cause disease once they are inside the human body. This led to a better understanding of the importance of antisepsis and sterilization. Before the 1900’s, surgical instruments were kept clean, but they were never sterile (clear of all microorganisms); as a result, many patients died after surgery. Microbiological research in Schick’s day led to the sterilization of surgical equipment, antiseptic treatment to keep all hospital rooms and equipment clean, and sanitation efforts aimed at keeping water supplies pure.

Bibliography

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