Lecture 1.2 -Introduction to microbes and infection

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Questions and Answers

What is the primary function of the capsid in a virus?

To provide a lipid bilayer membrane

To enable the virus to penetrate the host cell's cytoplasmic membrane

To facilitate the release of viral particles from the host cell

To protect the viral genome and proteins (correct)

Which of the following statements is true about enveloped viruses?

They are transmitted primarily through the faecal-oral route

They are more stable in adverse environments

They are more sensitive to harsh environments, such as heat and dryness (correct)

They are non-infectious and do not cause disease

What is the mode of transmission of non-enveloped viruses?

Parenteral route

Sexual route

Respiratory route

Faecal-oral route (correct)

How do antibiotics interfere with bacterial infections?

All of the above Signup and view all the answers

What is the key characteristic of coronaviruses (CoV)?

Positive sense, single-stranded RNA Signup and view all the answers

How do viruses replicate?

By using the host cell's machinery to synthesise viral components Signup and view all the answers

What is the primary site of viral replication in the laboratory?

All of the above Signup and view all the answers

What is the method of detection for the monkey pox virus?

PCR (Polymerase Chain Reaction) Signup and view all the answers

What is the role of viral enzymes or host enzymes in the replication process of a virus?

To remove the viral capsid and release the genome Signup and view all the answers

Where does the transcription and replication of DNA viruses occur?

In the nucleus Signup and view all the answers

What is the function of RNA-dependent RNA polymerase in negative sense RNA viruses?

To convert negative sense RNA to positive sense RNA Signup and view all the answers

What is the characteristic of positive sense single-stranded RNA viruses?

They can function as mRNA and get translated into proteins Signup and view all the answers

What is the term for a viral infection where the virus remains dormant within cells and does not cause symptoms until it is activated?

Latent infection Signup and view all the answers

What is the mechanism of penetration of a virus into a host cell?

Endocytosis of the viral particle Signup and view all the answers

What is the final step in the replication cycle of a virus?

Release of the viral particles from the host cell Signup and view all the answers

What is the characteristic of the human papilloma virus?

It is a non-enveloped DNA virus Signup and view all the answers

What is the term for the process by which a virus binds to a specific receptor on the host cell surface?

Haemagglutination Signup and view all the answers

What is the characteristic of prions?

They are infective proteins with no nucleic acid Signup and view all the answers

Which of the following is a type of helminth?

Taenia saginata Signup and view all the answers

What is the disease caused by Plasmodium falciparum?

Malaria Signup and view all the answers

Which of the following is NOT a type of protozoa?

Aspergillus Signup and view all the answers

What is the disease caused by Epstein Barr virus?

Infectious mononucleosis Signup and view all the answers

What is the characteristic of trematodes?

They are small, flat leaf-like worms Signup and view all the answers

What is the disease caused by Trypanosoma brucei?

Sleeping sickness Signup and view all the answers

Study Notes

Bacterial Infections

Treatment of bacterial infections involves antibiotics, which interfere with:
- Cell wall synthesis
- Protein synthesis
- Nucleic acid synthesis
- Cell membrane function

Viruses

Viruses are intracellular obligate parasites with:
- Genetic material that is RNA or DNA
- Enveloped or non-enveloped structure
- Capsid symmetry that can be helical or icosahedral, giving viruses their shape
Envelope: a lipid bilayer membrane acquired from the host cell cytoplasmic membrane
Capsid: a protein coat for the viral genome and proteins

Properties of Enveloped and Non-Enveloped Viruses

Enveloped viruses are more sensitive to harsh environments (e.g. heat, dryness) and are generally transmitted by:
- Respiratory routes
- Parenteral routes
- Sexual routes
Non-enveloped viruses are more stable in adverse environments and are generally transmitted by:
- Faecal-oral route

Specific Viruses

Coronaviruses (CoV):
- Enveloped
- Positive sense
- Single stranded RNA
- Infect humans, other mammals, and avian species
Monkey pox virus:
- Same family as variola virus (small pox)
- Same symptoms as small pox but milder and not fatal
- Spread through direct contact with monkey pox rash and scabs, as well as contact with saliva, upper respiratory secretions, and areas around the anus, rectum, or vagina
- Detected by taking a swab from lesions and PCR

Virus Growth

Viruses need living cells to replicate (obligate intracellular parasites)
They use the living cells to synthesize all the constituents of the virus
Different viruses grow in different types of cells
In the laboratory, viruses can be grown in:
- Vero cells
- HeLa cells
- Baby hamster kidney cells (BHK)

Steps in Viral Replication

Viruses undergo a similar sequence of events:
- Attachment to the appropriate cells
- Penetration of the virus into the cell (endocytosis or fusion of the envelope with the host cell membrane)
- Unloading of the viral capsid, releasing the genome and other materials into the host cell
- Replication: initiation of transcription or translation of the viral genome, resulting in the manufacture of virus components and genome
- Assembly of components into new viruses
- Release of the viruses by lysis or budding from the target cells

DNA Virus Replication

Transcription and replication occur in the nucleus of the infected cells
Most DNA viruses assemble in the nucleus
Early transcription (translation of proteins for DNA replication)
Late transcription (translation of structural proteins)
Assembly and release

RNA Virus Replication

RNA viruses normally undergo transcription, translation, and replication in the cytoplasm
Positive sense single-stranded RNA can function as mRNA and get translated into proteins by the host ribosomes
Negative sense RNA has to be changed to positive mRNA using the enzyme RNA-dependent RNA polymerase to make a positive strand copy, which can be read by the ribosomes and result in the manufacture of proteins

Latency

Latent viral infection: the virus can remain dormant within cells and does not cause symptoms until it is activated by some factors

Protozoa and Helminths

Protozoa: unicellular eukaryotic organisms
- Examples: Giardia lamblia, Cryptosporidium parvum, Plasmodium falciparum, Trypanosoma brucei
Helminths: multi-cellular organisms divided into three groups:
- Cestodes: ribbon-like, segmented intestinal parasites (e.g. Tapeworms)
- Nematodes: long, non-segmented worms (e.g. Roundworms)
- Trematodes: small, flat, leaf-like worms that can infect various organs (e.g. Flukes)

Prions

Unconventional infectious agents with no nucleic acid
Caused by infective proteins that accumulate in the grey matter and in extracellular amyloid plaques in the brain
Examples: Scrapie in sheep, Bovine Spongiform Encephalopathy (BSE) in cattle, Creutzfeldt-Jakob disease (CJD)

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Description

This quiz covers the basics of bacterial infections, their treatment with antibiotics, and the characteristics of viruses, including their genetic material and structure.