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Bacteria in History



Yersinia pestis growth on blood agar after 72 hours. Picture courtesy of CDC, Antlanta



We tend to think that the horrors of destroying and/or killing bacterial diseases belong into the past. Plague, Tuberculosis, Leprosy, Cholera … diseases which killed or disabled huge portions of the world population just died down! The bacteria, that causes these diseases are still there and minor outbreaks (at least ‘minor’ for now) happen.


LEPROSY

Mycobacterium leprae is the causative agent of the disease, leprosy, also known as Hanson's Disease. The bacterium was discovered in 1873 by a Norwegian physician named Gerhard Armauer Hansen. M. leprae is a gram-positive, aerobic rod surrounded by the characteristic waxy coating unique to Mycobacteria. In size and shape, it closes resembles M. tuberculosis. Leprosy has tormented humans throughout recorded history. The earliest possible account of a disease that many scholars believe is leprosy appears in an Egyptian Papyrus document written around 1550 B.C. Around 600 B.C. Indian writings describe a disease that resembles leprosy. In Europe, leprosy first appeared in the records of ancient Greece after the army of Alexander the Great came back from India and then in Rome in 62 B.C. coinciding with the return of Pompeii's troops from Asia Minor.
Throughout its history, leprosy has been feared and misunderstood. For a long time leprosy was thought to be a hereditary disease, a curse, or a punishment from God. Before and even after the discovery of its biological cause, leprosy patients were stigmatized and shunned. For example, in Europe during the Middle Ages, leprosy sufferers had to wear special clothing, ring bells to warn others that they were close, and even walk on a particular side of the road, depending on the direction of the wind. Since earliest history the person with leprosy has been shut out from society. Laws have prohibited marriage and allowed divorce of those with leprosy. Segregation of the sufferer from the rest of society has been followed by separation of the sexes, and of leprous parents from their children. Even in modern times, leprosy treatment has often occured in separate hospitals and live-in colonies called leprosariums because of the stigma of the disease. Leprosy has been so prevalent in various areas as certain times throughout history that is has inspired art work and influenced other cultural practices.




A photomicrograph of Mycobacterium leprae taken from a leprosy skin lesion. Picture courtesy of CDC, Antlanta





THE PLAGUE

The Swiss scientist Alexandre Yersin discovered the true cause of the plague. The bubonic plague, an infectious disease, are caused by microbes that invade the human body. The microbes that cause the plague are a type of bacteria known as the Yersinia pestis. The bubonic plague, however, does not start in humans. Instead it infects only rats and cannot be spread directly from rats to humans. Fleas, which live on the rats for food, abandon the rat when the rat dies. If the flees then find a human the Yersinia pestis is injected into the bloodstream. Then the disease can spread from man to man.
Black Death reached the shores of Italy in the spring of 1348 unleashing a rampage of death across Europe unprecedented in recorded history. By the time the epidemic played itself out three years later, anywhere between 25% and 50% of Europe's population had fallen victim to the pestilence.

Although some survived the painful ordeal, the manifestation of these lesions usually signalled the victim had a life expectancy of up to a week.
Having no defence and no understanding of the cause of the pestilence, the men, women and children caught in its onslaught were bewildered, panicked, and finally devastated.
Learned men and women, who did not believe that the plague was sent by god, attempted to come up with a more logical explanation. Some thought that the plague was brought by a "mysterious poisonous cloud" gradually moving across Europe. They attempted to prevent the plague from spreading by burning fragrant leaves and herbs to purify the air. While this improved the smell of garbage-filled cities and decaying bodies, it did nothing to stop the plague.

Physicians were not very helpful either. Medicine in the Middle Ages was based on astrology, religion and philosophical writings. The most common method of curing the plague was bloodletting (draining out the illness with blood). Cuts were made in various parts of the body, and the blood was left to run. Sometimes medicines were recommended that contained gold or powdered emeralds, which would most likely poison the patient further.



Mycobacterium tuberculosis Courtesy CDC


TUBERCULOSIS (TB)

Mycobacterium tuberculosis has been present in the human population since antiquity - fragments of the spinal column from Egyptian mummies from 2400 BC show definite pathological signs of tubercular decay.

The term phthisis, consumption, appears first in Greek literature. Around 460 BC, Hippocrates identified phthisis as the most widespread disease of the times, and noted that it was almost always fatal. Due to common phthisis related fatalities, he wrote something no doctor would dare write today: he warned his colleagues against visiting cases in late stages of the disease, because their inevitable deaths might damage the reputations of the attending physicians.

Exact pathological and anatomical descriptions of the disease began to appear in the seventeenth century. In his Opera Medica of 1679, Sylvius was the first to identify actual tubercles as a consistent and characteristic change in the lungs and other areas of consumptive patients. He also described their progression to abscesses and cavities. Manget described the pathological features of miliary tuberculosis in 1702. The earliest references to the infectious nature of the disease appear in seventeenth century Italian medical literature. An edict issued by the Republic of Lucca in 1699 states that, "henceforth, human health should no longer be endangered by objects remaining after the death of a consumptive. The names of the deceased should be reported to the authorities, and measures undertaken for disinfection."

In 1720, the English physician Benjamin Marten was the first to conjecture, in his publication, A New Theory of Consumption, that TB could be caused by "wonderfully minute living creatures", which, once they had gained a foothold in the body, could generate the lesions and symptoms of the disease. He stated, moreover, "It may be therefore very likely that by an habitual lying in the same bed with a consumptive patient, constantly eating and drinking with him, or by very frequently conversing so nearly as to draw in part of the breath he emits from the Lungs, a consumption may be caught by a sound person...I imagine that slightly conversing with consumptive patients is seldom or never sufficient to catch the disease." For the early eighteenth century, Dr. Marten's writings display a great degree of epidemiological insight.

In contrast to this significant level of understanding about the etiology of consumption, which was already enabling prevention and a break in the chain of infection, those attempting to cure the disease were still groping in the dark

The introduction of the sanatorium cure provided the first really step against TB. Hermann Brehmer, a Silesian botany student suffering from TB, was instructed by his doctor to seek out a healthier climate. He travelled to the Himalayan mountains where he could pursue his botanical studies while trying to rid himself of the disease. He returned home cured and began to study medicine. In 1854, he presented his doctoral dissertation bearing the auspicious title, Tuberculosis is a Curable Disease. In the same year, he built an institution in Gorbersdorf where, in the midst of fir trees, and with good nutrition, patients were exposed on their balconies to continuous fresh air. This setup became the blueprint for the subsequent development of sanatoria, a powerful weapon in the battle against an insidious opponent.

New advances then followed in rapid succession. In 1865, the French military doctor Jean-Antoine Villemin single-handedly demonstrated that consumption could be passed from humans to cattle and from cattle to rabbits. On the basis of this revolutionary evidence, he postulated a specific microorganism as the cause of the disease, finally laying to rest the centuries-old belief that consumption arose spontaneously in each affected organism.

In 1882, Robert Koch discovered a staining technique that enabled him to see Mycobacterium tuberculosis. What excited the world was not so much the scientific brilliance of Koch's discovery, but the accompanying certainty that now the fight against humanity's deadliest enemy could really begin.

The measures available to doctors were still modest. Improving social and sanitary conditions, and ensuring adequate nutrition were all that could be done to strengthen the body's defenses against the TB bacillus. Sanatoria, now to be found throughout Europe and the United States, provided a dual function: they isolated the sick, the source of infection, from the general population, while the enforced rest, together with a proper diet and the well-regulated hospital life assisted the healing processes.

These efforts were reinforced by the observation of the Italian Forlanini, that lung collapse tended to have a favorable impact on the outcome of the disease. With the introduction of artificial pneumothorax and surgical methods to reduce the lung volume, the depressing era of helplessness in the face of advanced TB was over, and active therapy had begun.

A further significant advance came in 1895 when Wilhelm Konrad von Rontgen discovered the radiation that bears his name. Now the progress and severity of a patient's disease could be accurately followed and reviewed.

Another important development was provided by the French bacteriologist Calmette, who, together with Guerin, used specific culture media to lower the virulence of the bovine TB bacterium, creating the basis for the BCG vaccine still in widespread use today. Then, in the middle of World War II, came the final breakthrough, the greatest challenge to the bacterium that had threatened humanity for thousands of years - chemotherapy.