Pharmaceutical Microbiology-Viruses.pptx

Pharmaceutical Microbiology

1. Viruses

2. General Structure of Viruses

3. Introduction Viruses are infectious agents so small that can only be seen at magnification. 10 t0 100 times smaller than most bacteria. They are incapable of independent growth in artificial media. Referred as Obligate intracellular parasites. Viral genetic material is either DNA or RNA. The structurally complete, mature and infectious virus is known as ‘ virion ’. Viral disease range from minor ailments such as the common cold to heighly fatal diseases such as AIDS or yellow fever. Viruses may cause mumps, rabies, influenza, measules or herpex simplex.

4. Difference Between Viruses, bacteria and Rickettsia Characteristics Viruses Typical Bacteria Rickettsia Intracellular Parasites + - + Plasma membrane - + + Binary fission - + + Both DNA and RNA - + + Filterable through bacteriological filters + - - ATP-Generation metabolism - + + Ribosome - + + Sensitive to antibiotics - + + Sensitive to interferon + - -

5. Classification Based upon multiplication in cells of different species: Bacterial viruses ( phagineae ) -They have DNA. Plant viruses ( phytophagineae ) -They have RNA and infect potato, sugarcane, tobacco, cucurbits etc. Animal viruses ( zoophagineae ) -Have DNA or some also have RNA and infect man, pigeon, parrot, dog, cow etc.

6. Classification Based upon physicochemical properties: (A) Primary Characteristics: 1. Chemical nature of nucleic acid - RNA or DNA 2. Structure of virion - Helical, icosahedral or complex 3. Site of replication – Nucleus of cytoplasm (B) Secondary Characteristics: 1. Host range – Specific host tissue or cell type 2. Specific surface structure - e.g. antigenic properties 3. Mode of transmission – e.g. feces

7. Classification Based upon physicochemical properties: (A) Primary Characteristics: 1. Chemical nature of nucleic acid - RNA or DNA 2. Structure of virion - Helical, icosahedral or complex 3. Site of replication – Nucleus of cytoplasm (B) Secondary Characteristics: 1. Host range – Specific host tissue or cell type 2. Specific surface structure - e.g. antigenic properties 3. Mode of transmission – e.g. feces

8. Classification Based upon family genera or species Class Nucleic acid Envelope Shape Example 1 . RNA viruses I (a) (+), ss RNA - Ecosahedral Picornaviruses I (b) (+), ss RNA + Ecosahedral Togaviruses II (-), ss RNA + Helical Paramyxoviruses III (-), ss RNA + Helical Orthomyxoviruses IV Ds, RNA - Ecosahedral Reoviruses V (+), ss RNA + Helical Retroviruses

9. Class Nucleic acid Envelope Shape Example 2. DNA viruses I (a) ds , linear DNA - Ecosahedral Adenoviruses I (b) ds, linear DNA + Ecosahedral Herpesviruses I (c) ds , linear DNA + Complex Poxviruses II ds , circular DNA + Ecosahedral Papovaviruses III ss , linear DNA - Ecosahedral Parvoviruses

10. Size of viruses Polio virus (30 nm) Adeno virus (90 nm)

11. Tobacco mosiac virus (250 nm) Rabies virus (100 nm)

12. Vaccinia virus (300 nm) Herpes simplex (100 nm)

13. Bacteriophages (225 nm)

14. Effect of Physical and Chemical Agents on Viruses Most human pathogenic viruses inactivated after exposure to 60°C for 30 min except serum hepatitis. Viruses are stable at low temperature and stored at -40°C to -70°C. UV light inactivate viruses. Lipid containing viruses inactivated by organic solvents such as chloroform and ether.

15. Life cycle of bacteriophages

16. Cultivation of Viruses

17. Embryonated E ggs

18. Tissue Culture Cell Culture Primary Diploid Continuous Organ Culture Explant C ulture