INTRODUCTION AND SCOPE
Microbiology is the study of living organisms of microscopic size. Medical microbiology is the subdivision concerned with the causative agents of infectious disease of man, the response of the host to infection and various methods of diagnosis, treatment and prevention. The term microbe was first used by Sedillot in 1878, but now is commonly replaced by microorganisms. Microorganisms include a large and diverse group of microscopic organisms that exist as single cell or cell clusters (e.g. bacteria, archaea, fungi, algae, protozoa and helminths) and the viruses, which are microscopic but not cellular.
IMPORTANCE AND RELEVANCE OF MICROORGANISMS
Microorganisms are relevant to all of our lives in a multitude of ways. Sometimes, the influence of microorganisms on human life is beneficial, whereas at other times, it is detrimental.
Beneficial Influence
- Production of important products: Microorganisms are required for the production of bread, cheese, yogurt, alcohol, wine, beer, antibiotics (e.g. penicillin, streptomycin, chloramphenicol), vaccines, vitamins, enzymes and many more important products.
- Contribution to public health: As aids to nutrition.
- Interruption of spread of disease: Other products are used to interrupt the spread of disease.
- Improving the quality of life: Still others hold promise for improving the quality of life in the years ahead.
- Component of an ecosystem: Microbes are also an important and essential component of an ecosystem. Molds and bacteria play key roles in the cycling of important nutrients in plant nutrition particularly those of carbon, nitrogen and sulfur. Bacteria referred to as nitrogen fixers live in the soil where they convert vast quantities of nitrogen in air into a form that plants can use.
- Energy production: Natural gas (methane) is a product of bacterial activity, arising from the metabolism of methanogenic bacteria.
- Cleaning up pollution: Microoragnisms are also being used to clean up pollution caused by human activities, a process called bioremediation (the introduction of microbes to restore stability to disturbed or polluted environments). Bacteria and fungi have been used to consume spilled oil, solvents, pesticides and other environmentally toxic substances.
Harmful Influence
- Microorganisms have also harmed humans and disrupted societies over the millennia. Microbial diseases undoubtedly played a major role in historical events, it was in the year 1347 when plague or ‘black death’ struck Europe and within 4 years killed 25 million people, i.e. one-third of the population.
- Many common human diseases are caused by bacteria, fungi (molds and yeasts), protozoa, helminthes.
Importance of Microbiology in nursing
- Diagnosis and treatment of infection: The role of the laboratory in assisting clinicians in the diagnosis of infection is to provide the physician wiht information concerning the presence or absence of microorganisms that may be involved in the infectious disease process. These individuals and facilities also determine the susceptibility of microorganisms to antimicrobial agents which plays role on the prescription of antibiotics or prophylaxis of infection and in monitoring antibiotic use.
- 4 Sterilization and disinfection: Advice is given on the adequacy of sterilization and disinfection procedures used elsewhere in surgical and medical practice and to test the efficacy of these processes in the laboratory. To do this, it is needed to understand the principles of operation of hospital sterilizing and disinfecting equipment, if or when testing may be of value, and how to carry out.
- Prophylaxis: In the final analysis, the patient's well-being and health can benefit significantly from information provided by the clinical microbiology laboratory for treatment or prophylaxis of infection.
- Diagnosis and control of hospital infection: An infection control team of workers, headed by the infection control doctor. The functions of this team include surveillance and control of infection and monitoring of hygiene practices, advising the infection control committee on matters of policy relating ot the prevention of infection and the education of all staff in the microbiologically safe performance of procedures. The infection control nurse is a key member of this team
THE DISCOVERY OF MICROORGANISMS
Antony van Leeuwenhoek (1632–1723)
The credit for having first observed and reported bacteria belongs to Antony van Leeuwenhoek. Antony van Leeuwenhoek, the Dutchman, was a draper and haberdasher in Delft, Holland. He was the amateur microscopist and was the first person to observe microorganisms (1673) using a simple microscope. In 1683, he made accurate descriptions of various types of bacteria. Their importance in medicine and in other areas of biology came to be recognized two centuries later.
SCIENTIFIC DEVELOPMENT OF MICROBIOLOGY
The development of microbiology as a scientific discipline dates from Louis Pasteur, perfection on microbiological studies by Robert Koch, the introduction of antiseptic surgery by Lord Lister and contributions of Paul Ehrlich in chemotherapy.
Louis Pasteur (1822–1895)
Louis Pasteur (1822–1895) was born in the village of Dole, France on December 27, 1822. He was originally trained as a chemist, but his studies on fermentation led him to take interest in microorganisms. Louis Pasteur is known as “Father of Microbiology” (Fig. 1.1).
Contributions of Louis Pasteur in Microbiology (Box 1.1)
Joseph Lister (1827–1912)
Joseph Lister was a professor of Surgery in Glasgo Royal Infirmaty. He was impressed with Pasteur’s study on the involvement of microorganisms in fermentation and putrefaction.
Developed a system of antiseptic surgery: He developed a system of antiseptic surgery designed to prevent microorganisms from entering wounds.
Father of modern surgery: He established the guiding principle of antisepsis for good surgical practice and was milestone in the evolution of surgical practice from the era of ‘laudable pus’ to modern aseptic techniques. For this work, he is called the “Father of modern surgery”.
Robert Koch (1843–1910)
Robert Koch (Fig. 1.2) was the German physician and is known as "Father of bacteriology”.
Contributions of Robert Koch
- Hanging drop method: He was the first to use hanging drop method by studying bacterial motility.
- Devised methods for isolating pure cultures of bacteria.
- Discovered the causal agents of anthrax (1876), tuberculosis(1882), and cholera (1883).
- Koch’s postulates: Robert Koch criteria for proving the causal relationship between a microorganism and a specific disease are known as Koch’s postulates (1876) (Box 1.2).
- Koch’s phenomenon: Koch (1890) observed that a guinea pig already infected with the bacillus responded with an exaggerated response when injected with the tubercle bacillus or its protein. This hypersensitivity reaction is known as Koch’s phenomenon.
Discovery of Viruses
As a science, virology evolved later than bacteriology.
Immunity and Immunization
Edward Jenner (1749–1823)
The first scientific attempts at artificial immunizations in the late 18th century by Edward Jenner(1749–1823) from England. Edward Jenner is known as the “Father of Immunology”.
Antibiotics—A Fortunate Accident—Sir Alexander Fleming (1881–1955) made accidental discovery that the fungus Penicillium notatum produces a substance which destroys staphylococci.
NOBEL PRIZES AWARDED FOR RESEARCH IN MICROBIOLOGY
The number of Nobel laureates in medicine and physiology for their contribution in microbiology is evidence of the positive contribution made to human health by the science of microbiology (Table 1.1).
IMPORTANT QUESTIONS
I. Write short notes on:
- Contributions of Louis Pasteur
- Contributions of Robert Koch
- Koch’s postulates