By Professor Barry C. Fox, M.D., University of Wisconsin
It is important to look back and think about where humankind would be today without the inventors and innovators whose inventions and discoveries are the foundations of modern medicine. A revolutionary aspect of medicine is the rapid molecular diagnostic testing for infectious diseases.
Rapid Molecular Diagnostic Testing
Rapid molecular diagnostic testing for infectious diseases has been revolutionizing medicine since the 19th century. In the 1800s, infectious disease germs were grown either in a liquid or a solid culture media that supported their growth. Germs were stained with the gram stain, to assist in their identification and classification.
Some disease conditions were highly suspicious of being caused by an infectious agent, but the hypothesis could not be proven. Laboratory studies were performed that were supportive, but not completely diagnostic. One such condition is known as “Whipple’s Disease”.
Whipple’s Disease
Whipple’s Disease is a rare chronic disease that involves multiple organ systems. Afflicted patients have a fever and generalized lymph node enlargement. Patients especially suffer from disturbances of the intestinal system that causes diarrhea and extensive weight loss.
The bacterium that causes this disease is known as “Tropheryma whipplei”. In 1943, Tropheryma whipplei, which was yet to be identified, was suspected to be a bacterium when pathology stains identified what appeared to be a bacillus or rod form.
In 1961, using the electron microscope, rod-shaped structures resembling bacteria were also seen in patients’ tissue specimens, providing additional support this illness might be infectious.
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Polymerase Chain Reaction
In 1992, scientists used a newly developed molecular diagnostic technique known as the polymerase chain reaction, or PCR, to multiply the ribonucleic acid, or RNA, from the ribosomes of 10 Whipple’s disease patients.
The PCR test showed identical positive results for all 10 patients, but not for the patients with other diseases. In 2000, scientists were finally able to isolate and grow Tropheryma whipplei from affected patient tissues using special primitive tissue cells known as “fibroblasts”. The PCR technology was the first important infectious disease molecular diagnostic technique.
The PCR Process
The PCR process is used to amplify specified sections of DNA or RNA. It begins with a few fragments of DNA or RNA and repeatedly cloning the DNA or RNA until there are millions of copies of a specific genetic sequence. This leads to a unique identification of a specific germ that can be either bacterial, viral, fungal, or other.
In 1983, scientist Kary Mullis invented this technique in collaboration with another scientist, Michael Smith. Another feat of modern medicine is the Matrix-Assisted Laser Desorption and Ionization, or MALDI. In this molecular diagnostic technique, the unique vapor profile of the germ is identified by vaporizing the biomolecules.
These two tests continue to advance the diagnosis and treatment of infectious diseases to new, almost unlimited boundaries.
This is a transcript from the video series An Introduction to Infectious Diseases. Watch it now Wondrium.
Hippocrates: Father of Modern Medicine
Greek physician Hippocrates is also known as the “Father of Modern Medicine”. He founded the Hippocratic School of Medicine, a college that revolutionized the understanding of medicine in ancient Greece.
In his school, Hippocrates taught medical students the skills necessary to make detailed clinical observations, diagnoses, and prognoses. In Greek medicine, doctors believed that people’s makeup predisposed them to certain diseases. The human constitution could be broken down into four humors or vital fluids: Earth, Water, Fire, and Air.
The Humors of Human Constitution
In this ancient scheme, the Earth is linked to black bile—sediment of blood, which is important in metabolism, bone formation, and clotting. Water is linked to phlegm—representing clear fluids like plasma, saliva, and mucus, which lubricates and nourishes the body.
Fire is linked to yellow bile—which is produced by the liver and stored in the gall bladder. Yellow bile affects the intestinal system and digestive processing of fats and cholesterol. And finally, Air—which is linked to red blood cells, and is thought to be the purest humor since it is essential for vitality and growth.
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Imbalance of Humors of Human Constitution
It was believed that if one of these humors was out of balance, it led to illness and disease.
Additionally, each humor was associated with a particular season and psychological temperament. For example, air in blood was linked to spring, which was associated with optimism and well-being. Hippocrates believed that physical health and individual personalities were part of a person’s entire health.
The negative characteristics of the humors were thought to come out only when there was excess or aggravated by imbalances. Excess in one humor led to the practice of bloodletting that was supposed to expel harmful surpluses of one of the humors.
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An Important Contribution of Hippocrates
An important contribution of Hippocrates was his recognition that specific diseases come from unique causes. During Hippocrates’s time, the Greek society believed that disease was the result of miasma or bad air or was due to superstitions or works of the gods as punishments.
Since the government forbade dissection of bodies, it was difficult to accurately study diseases. Hippocrates’s beliefs went against those of the government, and he was imprisoned for 20 years for his ideas and beliefs. However, there was a positive outcome to his imprisonment. During this period, he was able to write an important medical book, The Complicated Body, which set the course for the future of modern medicine.
Common Questions about Modern Medicines
Whipple’s Disease is a rare chronic disease in which afflicted patients have a fever and generalized lymph node enlargement. Patients especially suffer from disturbances of the intestinal system that causes diarrhea and extensive weight loss.
The ancient Greek physician, Hippocrates, is known as the “Father of Modern Medicine”.
According to Hippocrates, the human constitution could be broken down into four humors: Earth, Air, Fire, and Water.
