Antibiotics - Part 3

Question 1

What are the four main ways antibiotics can develop resistance?

Answer 1

• They can produce enzymes that inactivate or modify antimicrobials (e.g. beta-lactamases)
• They can change the drug target so that the antibiotic no longer has any effect
• Decreasing the permeability of the cell to the drug, meaning the concentration required for the drug to be effective is not achieved
• Bacteria are able to export the drug from inside the cell and the drug is usually exchanged for protons

Question 2

How do bacteria develop the four main resistance traits?

Answer 2

• Chromosomal resistance when a spontaneous mutation occurs and is passed onto all a cells progeny
• Acquires a mobile piece of DNA (i.e. from plasmids) and can transfer between cells of the same and of different species. Conjugation requires cell to cell contact between two bacteria. Small pieces of DNA called plasmids are transferred.
• Transformation is where a bacterial cell dies and its cell wall is broken down. The DNA within that bacteria is released into the environment and some bacteria can pick up pieces of this loose DNA and if it has information for antibiotic resistance the new bacteria can pick this information up along with it.
• Viral particles that can infect bacteria can carry genes of antibiotic resistance which they can transfer to the bacteria

Question 3

What is vertical gene transfer?

Answer 3

• Genetic information is passed from parent cell to progeny via binary fission

Question 4

What is horizontal gene transfer?

Answer 4

• Genes are transferred other than through traditional reproduction

Question 5

What are non-genetic mechanisms of resistance?

Answer 5

• Protected environment (e.g. body walls off the area of infection)
• Resting stage (most antibacterial agents look at turnover of bacteria so by resting the antibiotics are less effective)
• Presence of a foreign body