Answer :
Final answer:
A Gram-positive bacterial strain resistant to two antimicrobials could use the following mechanisms: altered drug targets, increased drug permeability, or overexpression of efflux pumps. Thus, the correct answer would be 'All of the above'.
Explanation:
The correct option is option B). The possible resistance mechanisms a Gram-positive bacterial strain could have when showing resistance to Drug A, targeting cell wall synthesis, and Drug B, targeting ribosomes, are:
- Altered drug target: The bacteria may mutate the gene encoding for the drug's target protein, rendering the drug ineffective, such as alteration in penicillin-binding proteins for resistance to ß-lactams.
- Increased drug permeability: Bacteria could alter membrane porins, reducing the uptake of antibiotics and preventing them from reaching effective concentrations inside the cell.
- Efflux pump overexpression: The bacteria can utilize efflux pumps to actively transport antibiotics out of the cell, lowering drug concentrations to sub-therapeutic levels.
Considering these mechanisms, the most comprehensive answer to the question of what resistance mechanisms the bacterial strain could have would be D) All of the above.