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 • • • • • 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 (Epstein Barr 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.