Historical Perspective



Historical Perspective


Eamonn V. Hoxey



The use of disinfection, preservation, and sterilization practices to kill microorganisms or to prevent or inhibit their growth is as old as human civilization or even older. The use of specific treatments to eliminate microorganisms and prevent deterioration or infection predates knowledge of the existence of living entities at a microscopic scale and has had a significant effect on health and welfare. Such treatments include those that have enabled development of animal husbandry and food preservation techniques to increase food production dramatically and create a safe food supply chain. Developments in public health and medical practices have decreased the occurrence and severity of infection, decreased morbidity and mortality, and improved the quality of life.

Developments in disinfection, preservation, and sterilization can be separated into three phases:



  • Serendipitous—random actions prior to the discovery of microbes identified procedures that benefited human health, allowed food to be stored for longer, or improved animal welfare. Without understanding the reason for their effectiveness, these procedures became incorporated into routine practices that improved food supply and reduced illness and death.


  • Empirical—knowledge of microorganisms and their link with spoilage and infection allowed observation and studies into the cause of deterioration and infection. Careful observation led to the definition of standard processes with demonstrable beneficial effect.


  • Scientific—understanding the nature of inactivation of microorganisms, and the variables that influence it, allowed development of engineering control and monitoring of process variables. This has led to the development of optimized processes with risk-based, targeted outcomes.


SERENDIPITOUS DEVELOPMENTS

Preservation of food by heating, drying, smoking, salting, fermenting, acidifying, adding sugar, and impregnating with spices and aromatics has been used by people throughout history. The Bible sets out instructions that soldiers returning from battle were required to disinfect their equipment and clothing with heat, either exposed to fire or boiling water.1 Alexander the Great required his armies to boil their drinking water and bury feces. He is also reported to have ordered timber for bridge building to be covered with olive oil as a precaution against decay. This process was then followed in the Roman empire for all wooden construction that was exposed to severe moisture.2 In Biblical and medieval times, fire was used to destroy clothes and corpses of diseased people. Historical reports from the Great Plagues mentioned the clothes of victims being burnt. Physicians who attended patients suffering from plague were careful to clothe themselves in protective garments comprising gloves, mask, hat, and long coat (Figure 1.1).

Alcohol has a long history of use for disinfection. Wine was used liberally throughout history, both externally and internally, to heal all kinds of ailments. Whereas the concentration of alcohol in wine provides little value as an antiseptic, distilled spirits provided a higher concentration of alcohol. Guy de Chauliac’s Inventarium sive Chirurgia Magna (The Inventory, or the Great [work on] Surgery) reported the use of brandy for military dressings. The title of the book is often shortened to Chirurgia Magna; it was written in medieval Latin in 1363 and circulated in manuscript form before its first printing in 1478.3 It was a compendium from previous authors with the addition of his own experience. There were 70 editions as it became the most influential surgical text for over 200 years, particularly in France.







FIGURE 1.1 Plague physician’s protective clothing, 17th century. From Father Maurice de Toulon, Traite de la Peste. Geneva, 1721. Courtesy of the Wellcome Collection.


EMPIRICAL DEVELOPMENTS

The first true observations of the killing of microorganisms by chemicals dates from 1676. Antonie van Leeuwenhoek4 (Figure 1.2) first observed viable organisms on a microscopic scale and reported that pepper and wine vinegar would kill microorganisms. Edmund King5 followed up the work of van Leeuwenhoek by testing a number of substances including sulfuric acid, sodium tartrate, salt, sugar, wine, blood, and ink. He observed their effect on rate of kill, mobility, and shape of the organisms.

Methods of preservation of wood were standardized earlier than disease-preventive treatments for plants, animals, and humans. For example, the first patent for a wood preservative containing “the Oyle or Spirit of Tarr” was granted in 1716 for the protection of ship planking against decay and shipworm.6 Coal-tar creosote, regarded as the standard wood preservative, was patented in 1838 with the injection of creosote under pressure into wood.7






FIGURE 1.2 van Leeuwenhoek sketches of microorganisms, bacteria isolated from the teeth and sketched in 1684.

The cause of contagious fungal disease in plants and the means of its prevention by treatment with chemicals were discovered before disease in humans because the results of growth of fungal pathogens could be seen directly with the naked eye. Tillet8 showed that chemicals in the form of saltpeter (potassium nitrate or other nitrogen-containing compounds) and lime (calcium oxide or calcium hydroxide) partially protected wheat seeds from infection by the bunt fungus. Prevost9 used copper salts in field tests and demonstrated that they prevented the germination of fungal spores. Sulfur was used to prevent fungus disease of plants as early as 1802, and the effective lime-sulfur protective treatment was introduced in 1851.10,11

In 1718, Joblot12 sterilized a hay infusion by boiling it for 15 minutes and then sealing the container. Appert13 applied this procedure for preserving food to develop canning food by combining heat and closed containers. Spallanzani14 noted that microorganisms in a liquid could be killed by heat and found that some organisms were more resistant than others; to kill resistant organisms, the liquid had to be boiled for 1 hour.

Semmelweis published his detailed observations15 in 1847 and later compiled a seminal book, Aetiologie,16 on his studies (Figure 1.3). He observed that when medical students came directly from the autopsy room and examined patients in the maternity ward, the rate of infection was greater than when students were not present. He noted odor from the autopsy room when students were present and insisted that they wash their hands with chloride of lime on leaving the autopsy room and before examining obstetric patients. The decrease in the death rate was spectacular.







FIGURE 1.3 Ignaz Semmelweis (1818-1865) and the title page of his book on Aetiologie from 1861.

Louis Pasteur’s experiments helped create the science of microbiology and inspired other scientists to investigate microbial diseases and the preservation of food and beverages. Pasteur (Figure 1.4) had to convince physicians that microorganisms cause disease. He advised surgeons to put their instruments through a flame before using them. He encouraged hospital personnel to heat sterilize bandages that were to be put on open wounds. He developed a process of heating wine briefly at 50°C to 60°C to prevent it being rejected because of off-flavors resulting from bacterial fermentations; a procedure now called pasteurization and still used for milk and other products.17






FIGURE 1.4 Pioneers in disinfection.

Lister18 (see Figure 1.4) attributed the inflammation of wounds in compound fractures initially to microorganisms in the air but later recognized that microorganisms on surgeon’s hands and dirty instruments were major causes of infection. He instituted a system of antiseptic surgery using phenol applied to the wound and to the floors and the walls of the operating rooms and wards. Lister commented that before antiseptic surgery, his wards were among the unhealthiest in the Glasgow hospital but, after the adoption of antiseptic treatment, the wards changed “so that during the last nine months not a single instance of pyemia, hospital gangrene, or erysipelas has
occurred in them.”18,19 Lister went to the United States in 1876 and lectured to the International Medical Congress. In the audience for his lectures was Robert Johnson, who started producing the gauze dressings soaked in phenol that Lister was using. This was the founding of Johnson & Johnson20 as a provider of surgical dressings and sutures. In 1888, Fred B. Kilmer,21 who had joined Johnson & Johnson, published a pamphlet and catalogue of products entitled Modern Methods of Antiseptic Wound Treatment with notes and suggestions from 10 eminent American physicians.

Robert Koch22 (see Figure 1.4) introduced modern bacteriology with sterile technique, pure cultures, solid media, and antimicrobial test methodology. Using the achromatic microscope, Koch demonstrated that bacteria invaded tissues to produce disease. He wrote a comprehensive research paper titled Uber Disinfektion (or “On Disinfection”)22 that described the ability of over 70 chemicals at different concentrations and at different temperatures to kill Bacillus anthracis spores.

Kronig and Paul23 established the basis of modern, scientific knowledge of the inactivation of microorganisms. They noted that



  • Bacteria exposed to an inimical agent are not all killed at a fixed time but at a rate that depends on the concentration of the agent and the temperature.


  • Inimical agents can be compared only when tested under controlled conditions, including challenge with a constant the number of microorganisms without interference from organic matter.


  • Action of the inimical agent must be arrested promptly after a stated period.


  • Surviving bacteria have to be transferred to the most favorable medium at optimal temperature.


  • Results are determined by accurate count of survivors on plate cultures.


SCIENTIFIC DEVELOPMENTS

The pioneering work of Kronig and Paul23 established the scientific principles for standardization of tests for chemical disinfectants and the detailed investigation of the inactivation of a population of microorganisms. This investigation of microbial inactivation has been undertaken on innumerable occasions in academia, health institutions, research centers, and industry and has involved researchers in a variety of fields from health care to defense and space exploration to food science. These studies have led to an understanding of the nature of microbial inactivation and the influence of experimental variables on the effectiveness of disinfection, preservation, and sterilization. This, in turn, has led to the adoption of a risk-based measure to predicting the outcome of an applied process, with an emphasis on understanding and monitoring an optimized process rather than trying to measure process effectiveness by microbiological testing of resulting products.

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May 9, 2021 | Posted by in MICROBIOLOGY | Comments Off on Historical Perspective
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