Identify the selection pressure on host or pathogen, trace survival and reproduction of the advantageous variant and explain the resulting counter-selection.
Methicillin-resistant Staphylococcus aureus (MRSA) is a disease causing worldwide concerns.
Methicillin is one of the antibiotics to which this pathogen has developed resistance.
Castaneroxy A is a molecule extracted from the European chestnut tree, endemic to Southern Europe and Turkey.
The effects of Castaneroxy A have been investigated.
The investigations have found that Castaneroxy A:
- does not affect the natural skin flora
- prevents MRSA from producing toxins
- weakens the MRSA bacteria
- reduces the size of skin infections caused by MRSA.
Explain why the development of this drug is an example of an 'evolutionary race' between humans and this pathogen.
(2)
An explanation that includes the following points:
- because MRSA has developed \{antibiotic / methicillin\} resistance (1)
- so we have had to find new drugs that this bacteria is not resistant to (1)
NB ACCEPT pathogens / bacteria throughout
DO NOT ACCEPT immune for resistance throughout
ACCEPT spreading / increasing
ACCEPT that will destroy it
(2)