TBL Microbiology

Question 1

What is the specific component of Gram-Negative bacteria triggers innate immune response?

Lipopolysaccharide
Lysozyme
N-acetylglucosamine
N-acetylmuramic acid
Peptidoglycan

Answer 1

Lipopolysaccharide

Bacterial lipopolysaccharide, a cell wall component characteristic of Gram-negative bacteria, is a representative pathogen-associated molecular pattern that allows mammalian cells to recognize bacterial invasion and trigger innate immune responses.

Question 2

What types of genes could potentially increase the virulence of a virus?

Host genes that improve the immune response

Host genes that increase the replication rate of the virus

Host genes that reduce target receptor expression

Viral genes that counter antiviral therapeutics

Viral genes that increase the external lifetime of the virions

Answer 2

Host genes that increase the replication rate of the virus

If viral replication rate were to be increased then this would limit the amount of time for the host to mount an effective defence and therefore the virus would have an advantage, potentially increasing the virulence.

Question 3

If a bat act as the reservoir to a new virus and this virus then infect humans and adapt very rapidly to the new host, how would you describe this new virus?

Horizontal, Baltimore I

Horizontal, Baltimore VII

Latrogenic, Baltimore III

Zoonotic, Baltimore II

Zoonotic, Baltimore V

Answer 3

Zoonotic, Baltimore V

Since the new infection represents a spill over from bats to humans then this virus would be described as zoonotic. The observation that the virus is adapting to the new human host very quickly strongly implies a high mutation rate to achieve this and therefore you would suspect an RNA based virus. The Baltimore classification system is based on the viral genome and from the above this is Baltimore V.

Question 4

What is the mode of action of macrolides?

Alteration of cytoplasmic membrane structure

Inhibition of 70S ribosomes

Inhibition of 80S ribosomes

Inhibition of cell wall synthesis

Inhibition of folic acid synthesis and metabolism

Answer 4

Inhibition of 70S ribosomes

Macrolides, such as erythromycin and clarithromycin, are inhibitors or protein synthesis so they inhibit ribosomes. They are able to selectively inhibit bacterial ribosomes, that are 70S. 80S are human ribosomes.

Try to think of drug classes / drug names that are examples of the other mechanisms.

Question 5

What is the mode of action of co-trimoxazole (trimethoprim + sulphonamide)?

Alteration of cytoplasmic membrane structure

Inhibition of 70S ribosomes

Inhibition of 80S ribosomes

Inhibition of cell wall synthesis

Inhibition of folate synthesis and metabolism

Answer 5

Inhibition of folate synthesis and metabolism

These 2 antibiotics are classified as anti-metabolites antibiotics, as they mimic metabolites. In this particular case they mimic metabolites that are involved in the folic acid pathway – the enzymes responsible for this pathway bind to the antibiotics and get inhibited, breaking the synthesis of tetrahydrofolate and then decreasing synthesis of nucleic acids.

Think: why do we give these 2 antibiotics together? Can we give them separately?