A brief introductory overview of microbiology subject matter and what it includes. This presentation and the following was teaching undertaken for Allied Health Sciences BSc as part of my postgraduate degree.

1. Ms. Clemencia Tjazuko
MSc Medical Microbiology
Introduction to Microbiology

2. What is Microbiology?`
• Study of microorganisms that EXIST as Single
Cells or cell clusters and must be viewed individually
with the aid of a Microscope

3.  Medical microbiology is the study of microbes that infect
humans, diseases they cause, and their diagnosis,
prevention and treatment.
 Response of human host to microbial and other antigens
 Microbes are invisible to naked eye and in order to
visualize them special equipment is needed i.e.
microscope

4. Contributors to Microbiology
 Antony van Leeuwenhoek (1632-1723)
 1st to observe and describe single celled
organisms which he termed “animalcules”,
referred to now as microorganisms
 Using a single lens microscope constructed by him
 Described different morphohological forms of bacteria
 1st to record observations of muscle fibers, bacteria,
spermatozoa and blood low in capillaries

5. •Ignaz Semmelweis (1846)
•Concluded that purperal sepsis was transmitted by
contaminated hands of nurses and medical staff
•Prevented by washing hands in antiseptic solutions

6.  Edward Jenner
 Developed the first vaccine  smallpox
vaccine
 Used cowpox virus to immunize children against
smallpox
 Observed that milk maids who had
a milder form of cowpox were not
prone to smallpox
 1796 removed fluid of cowpox from milkmaid,
inoculated James Phipps and he came down with
cowpox

7.  Louis Pasteur (1822-1895)
 Father of Microbiology
 Introduced techniques of sterilization and
developed steam sterilizer
 Also contributed for vaccine development against
several diseases such as anthrax, fowl cholera and
rabies

8.  Discovery of attenuation and the development of live
vaccines
 He disproved the theory of spontaneous generation of
disease and postulated the ‘germ theory of disease’.
Stated that disease can not be caused by bad air/
vapour but by the microorganisms present in the air
 Liquid media concept  used nutrient broth to grow
microorganisms

9.  Joseph Lister (1867)
 Father of antiseptic surgery
 Observed that postoperative infections were
greatly reduced through use of disinfectants
such as carbolic acid during surgery to sterilize
instruments and to clean the wounds
 Robert Koch (1843-1910)
 He introduced staining techniques and methods
of obtaining bacteria in pure culture in pure
culture using solid media
 He discovered bacillus of tuberculosis (1882)
and cholera vibrio (1883)

10. Koch’s Postulates
 Criteria to proof that a microorganism isolated from a
disease was the causative agent of that infectious
disease. Conditions to be met:
1. Bacterium should be constantly associated with
lesions of the disease
2. Should be possible to isolate bacterium in pure
culture from the lesions
3. Inoculation of pure culture into animal should
produce lesions of the disease
4. Should be possible to re-isolate bacterium in pure
culture from lesions produced in animals

12.  Exceptions to Koch’s Postulates
 Application of postulates not always possible to
study all human diseases
 Some bacteria do not satisfy all four postulates
 Examples:
 Mycobacterium leprae and Treponema pallidum
can not be grown in vitro; but maintained in
experimental animals
 Nesseria gonorrhoeae: no animal model but grown
in vitro

13.  Roux and Yersin (1888)
 Identified a new method of pathogenesis with
discovery with pathogenesis of diphtheria toxin
 Toxins neutralised by anti-toxin

14.  Paul Erhlich (1854-1915)
 Father of chemotherapy
 First to report acid-fast nature of tubercle
bacillus
 Developed techniques to stain tissues and blood cells
 Proposed toxin-antitoxin interaction  Erlich
phenomenon and introduced methods of standardising
toxin and antitoxin

15.  Proposed the side chain theory for antibody production
 Chemotherapy: He discovered salvarsan (arsenical
compound) treatment for syphilllis
 Erlichia bacteria named after him

16. •Ersnt Ruska (1934)
•Developed the electron microscope enabling
visualisation of viruses

17.  Alexander Fleming (1929)
 Made accidental discovery that Penicillium (fungus)
produces a substance that destroys staphylococci.
 Further work with fungus by Florey and Chain at
Oxford led to isolation of active substance penicillin and
mass production
 This began the antibiotic era

18. Penicillium
S.aureus

19. Classification
 Why is it important to classify organisms?
 To enable easy identification by:
1. Grouping organisms with similar properties together
2. Separate those that are different from one another
 The basic taxonomic unit in bacteria is the species, two species
differ from each other in the various features determined by
genes.
 Bacterial taxonomy has three components:
1. Classification/orderly arrangement of units. Group of units is
called a taxon
2. Identification of unknown with defined and named unit
3. Nomenclature, or the naming units

20. Nomenclature
 Follows rules proposed by Carolus Linneaeus, a
Swedish botanist binomial nomenclature
 Scientific names for taxonomic levels above
genus are capitalized but not italicized e.g.
Phylum Proteobacteria
 Binomial nomenclature system: scientific name of
bacteria comprised of genus name and species
name. The genus and species name should be
italicized or underlined e.g. Staphylococcus
aureus or Staphylococcus aureus

21.  Genus and species coined based on property of
the bacteria:
 S.aureus- named after arrangement in cluster
and type of pigmentation produced
 Nesseria meningiditis- named after discoverer of
disease U. Neisser and disease it causes
meninigitidis
 Brucella suis and Brucella melitensis- named
after discoverer (David Bruce), host (suis) and
place of discovery (Malta, Europe).

22. Branches of Microbiology
 Bacteriology - study of bacteria
 Virology – study of viruses
 Mycology – study of fungi
 Parasitology – study of parasites
 Immunology – study of immunity

23. Bacterial Classification
 Kingdom- divided into division, class, order, family,
tribe, genus and species. Properties of a population
studied and not individual.
 Population derived by binary fission from single cell
(clone)
 Clone- single bacterial cell. Most are identical
 Population of bacteria derived from particular source
e.g. patient is called a strain

24. Bacteria
Size:
0.2-1.5 by 3-5 µm
Important Characteristics:
 Prokaryotic
 Unicellular
 Simple internal structure
 Grow on artificial laboratory media
 Asexual reproduction (mostly simple cell division)
Significance:
 Cause of disease

26. Viruses
Size:
0.015-0.2 µm
Important Characteristics:
 Do not grow on artificial media but require living cells
within which they reproduce
 Obligate anaerobes
 Electron microscope required to observe
Significance:
 Cause diseases
 Also infect microorganisms

28. Fungi (Yeasts)
Size:
5.0-10.0 µm
Important characteristics:
 Eukaryotic
 Unicellular
 Grow on artificial laboratory media
 Reproduction is asexual (cell division/budding) or sexual
Significance:
 Cause disease

30. Fungi (Molds)
Size:
2.0-10.0 µm by several mm
Important characteristics:
 Eukaryotic
 Multicellular
 Distinctive structural features
 Cultivated on artificial cultural media
 Reproduction is asexual or sexual
Significance:
 Cause disease

32. Protozoa
Size:
2.0-200 µm
Important Characteristics:
 Eukaryotic
 Unicellular
 Some can be cultivated on artificial media while some
are intracellular parasites
Significance:
 Some cause disease

34. Type Cultures
 International reference laboratories designated as
type culture reference centers
 Maintain representative cultures of established
species, show characteristics of original strain
 Strains isolated in labs compared using standard
strains supplied by type culture centers
 Important:
1. ATCC – American Type Culture Collection (USA)
2. NCTC – National Collection of Type Cultures (UK)

35. Questions
1. Define medical microbiology
2. What are the branches of microbiology?
3. Who is the Father of Microbiology?
4. What are the Koch’s postulates?
5. How to name microorganisms?