Introduction And History

Medical Microbiology Introduction and History: 9 9

Different forms of life exist on earth. Animals, human beings, plants, which are visible to naked eye and are called macro-organisms. Other forms of life invisible to naked eye are called micro-organisms, (micro = small, bious = life). Microbiology is the science that deals with the study of microorganisms and their activities. The term was introduced by the French chemist Louis Pasteur. Microorganisms are studied with reference to their: • • • • • • • •

9

9 9 9

9

9 9

Form and structure Reproduction Physiology and metabolism Identification Distribution in nature Relationship with each other and with other living organisms Beneficial and detrimental effects on human beings and animals Physical and chemical changes induced by them in their environment, etc.

Animal and plant cells can exist only as parts of animals and plants. In contrast, microbial cells are generally able to carry out their activities such as growth and multiplication, generation of energy and reproduction independently. Microorganisms are found everywhere in nature (air, water, food, soil, sewage, lakes, sea, etc.). They are also present in and on our body-on the skin and mucous membranes, in gastrointestinal and urogenital tracts and other parts of the body. The place/environment where a microorganism normally lives is known as Habitat.

Some possess plant-like characters, while others have animal-like characters and few of them are altogether different. Based on morphological and functional properties, they are grouped as: • Bacteria are small, unicellular, microscopic organisms with primitive nucleus • Fungi are unicellular or multicellular microscopic organisms with well-developed nucleus. They possess plant-like characters but are devoid of chlorophyll and are not differentiated into roots, stem, leaves, etc. • Algae are unicellular or multicellular microscopic organisms possessing plant-like characters. They possess chlorophyll but are not differentiated into roots, stem, leaves, flowers, etc. Most of them possess well-developed nucleus, except blue green algae • Protozoa are unicellular, nonphotosynthetic microscopic organisms possessing animal-like characters, i.e. they do not possess rigid cell wall. They have a well developed nucleus • Viruses are very small, ultramicroscopic (seen under electron microscope), noncellular microorganisms capable of multiplying only inside the living cell. They are different from other living creatures Various branches of Medical Microbiology are: Features of Microbes • General Microbiology • Immunology M = Microscopic • Bacteriology I = Independent units • Virology C = Complex (less) • Mycology R = Rapid growth rate • Parasitology O = Omnipresent • Clinical Microbiology Medical Microbiology is the branch of microbiology that deals with the study of disease-producing microorganisms in human beings. It also includes prevention and control of the disease. Paul Ehrlich is known as the father of Chemotherapy

CONTRIBUTIONS OF LOUIS PASTEUR: • Microbial theory of fermentation and proving that all forms of life including microorganisms arise from their like and not spontaneously • Principles and practice of sterilization

• Development of initial bacteriological techniques • Control of diseases of silkworms • Development of vaccines against: o Anthrax o Chicken cholera o Rabies CONTRIBUTIONS OF ROBERT KOCH: • Verification of germ theory of diseases • Introduction of staining techniques for visualization of microorganisms • Discovery and use of solid medium in bacteriology • Discovery of causative agents of: o Tuberculosis o Cholera o Anthrax • Koch's postulates • Use of laboratory animals for experimental infections KOCH’S POSTULATES: Robert Koch postulated the criteria for proving that a microorganism isolated from a disease was indeed causally related to it. According to these postulates, a microorganism can be accepted as the causative agent of the disease only if following conditions are satisfied: • The microorganism should be constantly associated with the lesions of the disease • It should be possible to isolate the organism in pure culture from the lesions of the disease • Inoculation of such pure culture in suitable laboratory animals should produce a similar disease in animals • It should be possible to reisolate the organism in pure culture from lesions produced in the experimental animals • An additional criteria introduced subsequently requires that-specific antibodies to that organism should be demonstrable in the serum of patients • These postulates have proved to be useful in confirming doubtful claims made regarding the causative agents of infectious diseases. CONTRIBUTIONS OF PAUL EHRLICH: • Discovery of salvarsan as a chemotherapeutic agent against syphilis. This opened the new field of antimicrobial agents which has saved the lives of millions of people till date. • Identified that mycobateria have acid fastness nature • Proposed a theory for the production of antibody called as "side chain theory" • Refined the science of staining the organisms • Advocated standardization of biologicals including toxins and antitoxins to ensure uniformity Scientists and their contributions: Year 1850 1874 1879 1881 1882 1883 1884 1885 1886 1886 1887 1887 1892 1892

Scientists Davaine and Pollender Hansen Neisser Ogston Robert Koch Robert Koch Loeffler Nicolaier Frankel Escherich Weichselbaum Bruce Pfeiffer Welch and Nuttall

Discoveries Anthrax bacilli Lepra bacilli Gonococci Staphylococci Tubercle bacilli Cholera bacilli Diphtheria bacillus Tetanus bacilli Pneumococci E. coli Meningococci Brucella Influenza bacilli Clostridium welchii

1894 1896

Yersin and Kitasato Shiga

Plague bacilli Shigella

ROLE OF MEDICAL MICROBIOLOGY Medical microbiology plays an important role in the diagnosis, prevention, treatment and control of infectious diseases. Some of the applications of medical microbiology are: • Confirmation of diagnosis which helps in starting specific treatment • Detection of newer pathogens • Determination of antimicrobial susceptibility patterns • Development of vaccines and immunotherapeutic agents • To trace the source/reservoir of infection • To trace the route of spread of pathogens using epidemiological markers such as gene sequencing • Monitoring of changing profile of pathogens • Distinction between recent and past infections • Monitoring the quality of air, water and food