Pathogenic Properties of Virus

• •  Viruses have mechanisms to evade host defenses viruses grow inside host cells to hide from immune defense.

•  Kill immune cells e.g. HIV – TH Cells.

•  Cytopathic effects: - The visible effects of viral infection on host cell. Some effects will kill the cell and some will just change the cells.

•  Viruses stop DNA, RNA and/or protein synthesis e.g. Herpes virus block mitosis.

•  Lysosomal autolysis of host cells e.g. Influenza: bronchiolar epithelium.

•  Production of inclusion bodies (visible viral parts inside the cell) can identify a particular virus e.g. Rabies virus: Negri bodies.

•  Syncytium formation (neighboring cells fuse together) e.g. Varicella Zoster virus.

•  Change in cell function e.g. Measles, production of interferons by host cell (triggers host immune response), induce antigenic changes on host cell surface (triggers destruction of infected cell by host immune response).

•  Induce chromosomal changes, cell transformation: may activate or deliver oncogenes resulting in loss of contact inhibition (cancer) e.g. Papilloma virus.

 

Eukaryotic Pathogens  

Fungi

• •  They produce toxins causing allergies or disease e.g. -chronic sinusitis (black molds).

•  Stachybotrys : headaches, vomiting, mental disturbance.

•  Invasive systemic mycosis in immune compromised patients e.g. Candida.

•  Mushrooms: mycotoxins may be hallucinogenic or deadly.

Protozoa:  

• •  They can grow inside host cells causing lysis e.g. Malaria (Plasmodium)

•  They use host cells as food source and produce wastes that cause disease.

Algae: - It produces neurotoxin substances e.g. shellfish poisoning

REFERENCES:

Text Books:

1. Jeffery C. Pommerville. Alcamo's Fundamentals of Microbiology (Tenth Edition). Jones and Bartlett Student edition.

2. Gerard J. Tortora, Berdell R. Funke, Christine L. Case. Pearson - Microbiology: An Introduction. Benjamin Cummings.

Reference Books:

1. Lansing M. Prescott, John P. Harley and Donald A. Klein. Microbiology. Mc Graw Hill companies.

2. Biology, Raven and Jhonson, 6 th edition (2001)

3. Microbiology, Pelczar. M.J , Chan E.C.S, Kreig N.R, 5th edition (2007)