Antibiotic Resistance Flashcards
What is selection pressure
Selection pressure is a variable that reduces reproductive success in population e.g disease, predators
What is allele frequency
Allele frequency is number of times a single allele occurs in population’s gene pool
What is process of evolution
Process of evolution is:
organisms produce more offspring than can survive, causing competition.
Naturally occurring variation within population, with random mutations creating new alleles
Change in environment causes change in selection pressure
Those with advantageous allleles more likely to survive and reproduce
May pass on favourable alleles to offspring
Overtime, advantageous allele frequency increases.
Why do bacteria become resistant to antibiotics
Bacteria become resistant to antibiotics because mutations with bacterial DNA could result in an allele that makes bacteria resistant to method of action by an antibiotic. These bacteria are more likely to survive antibiotic (selection pressure).Differential survival (some are more likely to survive than others)
These bacteria reproduce (by mitosis) and pass on allele for antibiotic resistance.
Overtime, allele accumulates in bacterial population.
What are causes of antibiotic resistance
Causes of antibiotic resistance are
Overprescribing antibiotics so more bacteria are exposed to antibiotics more often, more chances for mutations
Patients not finishing treatment, so bacteria which are slightly resistant survive and reproduce.
Poor infection control in hospitals/clinics
Why can bacteria evolve so quickly
Bacteria can evolve quickly because they reproduce very quickly, so more opportunities for mutations, that may result in antibiotic resistance.
Able to re-establish population size swiftly
Number of cells containing mutation is large (in billions)
What is horizontal evolution
Horizontal evolution is when:
Plasmid had gene for antibiotic resistance. 1 strand of (double stranded) plasmid DNA transfers between conjugating bacteria. Each bacteria replicated strand to make complete plasmid. Both bacteria now resistant.
What is bacterial conjugation
Bacterial conjugation is cell to cell contact between bacteria
Why do we still have diseases such as TB
We still have diseases such as TB because:
Antibiotic resistance
Evolutionary race between pathogen and host. Host evolves mechanism to combat pathogen e.g feature of immune system. Pathogen reproduces very quickly producing bacteria with mutations that give pathogen adv. may allow pathogen to overcome host immune system. E.g change in antigens
Evolutionary race between pathogens and drug developers
Drugs provide selection pressure. Rapid multiplication of bacteria produces mutations. Any with mutation that make them resistant to drug are more likely to survive and reproduce
What is 5 point plan for antibiotic resistance
5 point plan for antibiotic resistance:
Independent: type of antibiotic
DV: width of zone of inhibition measure diameter with a ruler graduated in mm
Distribute bacteria every by lawn spreading
Controlled variables: volume of agar (pipette)
48h incubation period at 18degrees
Same aseptic techniques used e.g sterilised pipette
Control: disc with no antibiotic
Repeat 5 times for mean results and then repeat with different bacteria
What should be said for exam questions on evolutionary race between bacteria/host
Mutation
Change in structure e.g antigens
Impacts immune response, secondary immune response not possible, memory cells will not recognise new antigen. New antigen must be presented
How can bacteria become resistant to method of action of antibiotic
Bacteria can become resistant to method of action to antibiotic by:
Mutation to allow enzyme to breakdown antibiotic
Mutation allowing bacteria to use different metabolic pathway for reactions inhibited by antibiotic.
