1. Introduction to Microbiology
Dr. Waleed Khalid
Lec. : 1

2. Medical microbiology is the study of the causative agents of infectious diseases of humans and the reaction to such infections. In other words it deals with etiology, pathogenesis, laboratory diagnosis, specific treatment and control of infection (immunization).

3. Medical microbiology includes:
Bacteriology – The science that study bacteria, the causative agents of a number of infectious diseases.
Virology – The science that study viruses, non-cellular living systems, capable of causing infectious diseases in human being.
Immunology – The science which concerned with mechanisms of body protection against pathogenic microorganisms and foreign cells and substances.
Mycology – The science that deals with the study of fungi .
Protozoology – It deals with pathogenic unicellular animal organisms.

4. Classification of Microorganisms:-
Classification by structure
Subcellular – DNA or RNA surrounded by a protein coat – viruses
Prokaryotic – simple cell structure with no nucleus or organelles – bacteria
Eukaryotic – complex cell structure with nucleus and specialized organelles – protozoans, fungi, parasites

5. Naming of Microorganisms:-
Standardized naming
Genus
Category of biologic classification
Example – Staphylococcus
Species of organism
Represents a distinct type of microorganisms
Examples – Staphylococcus aureus and Staphylococcus epidermidis
The genus name is written with a capital letter, and the species name – with a small letter.

6. How Microorganisms Cause Disease
Microorganisms cause disease in a variety of ways
1- By using nutrients needed by cells and tissues
2- By damaging cells directly
3- By producing toxins
These microorganisms may remain localized or become systemic
Transmission
Direct contact
Indirect contact

7. Localized symptoms Generalized symptoms Normal flora Swelling Fever
Pain
Warmth
Redness
Generalized symptoms
Fever
Tiredness
Aches
Weakness
Normal flora
Provides a barrier
Can cause an infection when the immunity decrease .

8. 1- Viruses They are the smallest known infectious agents
They are subcellular microorganisms that :
Have only nucleic acid surrounded by a protein coat
Must live and grow in living cells of other organisms
Hepatitis virus

9. Illnesses caused by viruses
Colds
Influenza
Hepatitis
Warts
AIDS
Vaccines are available for many viruses
Mumps
Rubella
Measles
Herpes

10. 2-Bacteria Classification 1- Shape 2- Ability to retain dyes
Single-celled prokaryotic organisms that reproduce rapidly .
Classification
Bacteria can be classified according to:-
1- Shape
2- Ability to retain dyes
3- Ability to grow with / without air
4- Biochemical reactions
Bacillus bacterial classification

11. Classification and Identification
1- Shape
Coccus – spherical, rounded, or ovoid
Bacillus – rod-shaped
Spirillum – spiral-shaped
Virbrio – comma-shaped

12. Spherical (cocci) bacteria
Micrococci
Diplococci
Streptococci
Staphylococci
Tetracocci
Sarcine

13. Representatives of pathogenic cocci1 2
1.Scanning Electron Micrograph of Streptococcus pneumoniae
2.Scanning electron micrograph of a Staphylococcus aureus

14. Electron Micrograph of Neisseria gonorrhoeae

15. Classification and Identification (cont.)
2-Ability to retain certain dyes
Gram’s stain
Acid-fast stain
3- Ability to grow in presence or absence of air
Aerobes – grow best in the presence of oxygen
Anaerobes – grow best in the absence of oxygen
4- Biochemical reactions

16. Special groups Chlamydiae
Mycobacteria – bacilli with a cell wall that differs from most bacteria
Rickettsiae
Very small
Live and grow within other living organisms such as mites and ticks
Chlamydiae
Cell wall structure differs from other bacteria
Live and grow within other living cells
Mycoplasmas – completely lack the rigid cell wall

17. The size of bacteria
The size of bacteria is measured in micrometer (m) or micron () (1 micron or micrometer is one thousandth of a millimeter) and varies from 0.1  to . Most pathogenic bacteria measure from 0.1 to 10 .
The other units of measurement of microorganisms is nanometer (nm) (one millionth of a millimeter) .

18. BACTERIAL CELL

19. FLAGELLA
Electron Micrograph of Bacteria with Flagella

20. SPORE
Bacillus anthracis
Bacillus megaterium

21. Cell wall
In addition to conferring rigidity upon bacteria, the cell wall protects against osmotic damage
Chemically, the rigid part of the cell wall is peptidoglycan
Cell wall first described by Gram in It is used to study morphologic appearance of bacteria. Gram's stain differentiates all bacteria into two distinct groups:
a. Gram-positive organisms
b. Gram-negative organisms

22. Gram
Staining
Technique

24. Protozoan Trichomonas vaginalis
3- Protozoans
Single-celled eukaryotic organisms, larger than bacteria, they are found in soil and water and they are a leading cause of death in developing countries
Illnesses caused by protozoans are
Malaria
Amebic dysentery
Trichomoniasis vaginitis
Protozoan Trichomonas vaginalis

25. 4- Fungi Eukaryotic organisms with rigid cell wall Yeasts
Yeast: a single-celled fungi
Eukaryotic organisms with rigid cell wall
Yeasts
Single-celled
Reproduce by budding
Molds
Large, fuzzy, multicelled organisms
Produce spores
Superficial infections
Athlete’s foot
Ringworm
Thrush
Can cause systemic infections

26. Multicellular Parasites
Organisms that live on or in another organism and use it for nourishment
Parasitic worms
Usually due to poor sanitation
Roundworms
Flatworms
Tapeworms
Parasitic insects
Bite or burrow under the skin
Mosquitoes
Ticks
Lice
mites

27. Very Good! Apply Your Knowledge ANSWER: Matching:
___ Yeast or mold A. Virus
___ Tapeworm / lice B. Bacteria
___ Classified by shape C. Protozoan
___ Subcellular organism D. Fungus
___ May be aerobic or anaerobic E. Multicellular parasite
___ Smallest known organism
___ Found in soil and water
Very Good! E B A B A C