Introduction to Microbiology Dr. Waleed Khalid Lec. : 1

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).

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.

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

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.

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

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 .

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

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

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

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

Spherical (cocci) bacteria Micrococci Diplococci Streptococci Staphylococci Tetracocci Sarcine

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

Electron Micrograph of Neisseria gonorrhoeae

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

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

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 16-18 . Most pathogenic bacteria measure from 0.1 to 10 . The other units of measurement of microorganisms is nanometer (nm) (one millionth of a millimeter) .

BACTERIAL CELL

FLAGELLA Electron Micrograph of Bacteria with Flagella

SPORE Bacillus anthracis Bacillus megaterium

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 1884. 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

Gram Staining Technique

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

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

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

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