evolving pathogens - Unit 4 AOS 2

Question 1

bacterial resistance to antibiotics

Answer 1

• Antimicrobial agents play an important role in protecting us from harmful pathogens. Just as we develop new and improved antimicrobial agents against pathogens, however, pathogens themselves are becoming better at fighting back against us.

Question 2

mechanisms of antibiotic resistance

Answer 2

• The formation of antibiotic-resistant bacteria can be attributed to the process of natural selection, where the exposure to antibiotics serves as an environmental selection pressure
• If bacteria with resistance to a particular antibiotic are present in the exposed population, then they will be conferred a selective advantage, allowing them to continue living and replicating within their host and increasing the allele frequency for antibiotic resistance.
• Conversely, those bacteria which are susceptible to the antibiotic are killed by the antibiotic.

Question 3

causes of bacterial resistance

Answer 3

• Variation and the emergence of new alleles conferring resistance against antibiotics is facilitated largely by mutations. Through mutations, new alleles can help bacteria develop mechanisms which increase their ability to combat the action of antibiotics.

other causes:
- stopping antibiotics: bacteria (potentially resistant bacteria) continue to spread
- using antibiotics for viral infections

Question 4

consequences of bacterial

Answer 4

• When bacteria become resistant, existing antibiotics are no longer effective, which increases the difficulty of treating infections caused by these bacteria.

Question 5

viruses adapting

Answer 5

• Just like bacteria, viruses are constantly adapting and changing, allowing them to increase their virulence and resistance against the immune system and existing medications.
• In particular, the surface antigens of viruses frequently undergo changes in an effort to avoid detection by immunological memory cells developed from past infection or vaccination on subsequent exposure.
• In doing so, any medications targeting specific surface antigens on the virus are also rendered ineffective. Therefore, it is extremely difficult to develop effective, long-term vaccinations and medications against viruses.

Question 6

antigenic drift

Answer 6

• involves small and gradual changes in the genes encoding for viral surface antigens. In the beginning, previous memory cells generated will be capable of recognising these mutated surface antigens.
• However, as the mutations continue to accumulate, a new subtype of virus can form, which will no longer be recognised by previously generated memory cells.

Question 7

antigenic shift

Answer 7

• involves sudden and significant changes in the genes encoding for viral surface antigens. This commonly occurs when two or more different strains of a virus combine when coinfecting the same host to form a completely new subtype through a process known as viral recombination.
• Natural immunity to this new virus subtype is likely to be uncommon, making it extremely infectious, with the potential to develop into an epidemic or pandemic.