Transcript Emerging Diseases

Emerging Diseases
Lecture 4:
Important Types of Germs
4.1: Overview
4.2: Characteristics of Germs
4.3: Summary
4.1: Overview
The germs that cause infectious
diseases are of various types.
Some are alive and are made of cells
but others are not alive = no cells.
Overview : Five Types of Germs and
Examples of their Diseases
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Parasites-tapeworms, amoebas, protozoa
Fungi- athlete’s foot, yeast infections
Bacteria-anthrax, syphilis, Staph infections
Viruses- AIDS, cervical cancer (HPV), influenza
Sub-viral pathogens- Mad Cow, Hepatitis D
List goes from largest in size to smallest
4.2: Characteristics of Germs- Parasites
Includes single-celled protozoa as
well as multicellular organisms
All “parasites” are Eukaryotes
May live within body cavities or may burrow
deep into soft tissues
Protozoa are very diverse-Plasmodium, Giardia,
Pneumocystis, Cryptosporidium
4.2: Characteristics of Germs- Fungi
Eukaryotic cells
May live in visible colonies or as individual cells
Specialists at living on other organisms
Cell wall made of chitin
4.2: Characteristics of Germs- Bacteria
Single prokaryotic cells
Living pathogens
Simple life style
Ready to take advantage of opportunity
Most have rigid cell wall, primitive types do not
e.g. mycoplasmas
4.2: Characteristics of Germs-Viruses
Nonliving, noncellular
Very small (electron microscope)
Simplest ones consist of only a few genes (RNA
or DNA) protected by a protein coat
Require cells to reproduce
4.2: Characteristics of Germs-Subviral
Pathogens
Nonliving, noncellular
Very small (electron microscope)
May be defective virus-like particles, or an
individual RNA or protein molecule
Require cells to reproduce
Prions-a type of infectious protein-are the most
famous
4.3. Summary-Parasites
Include protozoa such as Giardia lamblia-causes
Giardiasis or “beaver fever”
Protozoa are living, eukaryotic organisms that may
be single-celled or sometimes two-celled and
may have a cell wall.
Include multicellular parasitic worms such as Taenia
saginata the beef tapeworm
Parasitic worms are eukaryotic, multicellular
animals that do not have a true cell wall but may
have a tough outer coating, they usually
penetrate or attach to soft body surfaces.
4.3: Summary-Fungi
Include organisms classified as yeasts and molds
Fungi are living, eukaryotic organisms that may
be single-celled or sometimes live in colonies.
They have a special cell wall made of chitin.
Include Candida albicans causes “thrush” and
various species that cause diseases such as
athlete’s foot
4.3: Summary-Bacteria
Include organisms classified as true bacteria and as
mycoplasmas.
Bacteria are living, prokaryotic organisms that may
be single-celled or sometimes live in colonies.
Mycoplasmas are the simplest known living
organism. True bacteria have a cell wall but
mycoplasmas do not.
Bacillus anthracis is a bacterium that causes
anthrax.
Mycoplasma pneumoniae is a mycoplasma that
causes pneumonia.
4.3: Summary-Viruses
Non-living and do not contain cells.
Require cells for reproduction.
Include agents that cause diseases such as AIDS
(HIV-1), infectious mononucleiosis (EpsteinBarr Virus) and smallpox (Variola Virus).
4.3: Summary-Subviral Pathogens
Non-living and do not contain cells.
Require cells for reproduction.
Include agents that cause diseases such as prions
(infectious proteins) that cause Mad Cow Disease
and others.
Also includes agents such as the Hepatitis Delta
agent that causes Hepatitis D.