A Gram‑negative bacterial species
acquires mutations that reduce expression of outer‑membrane
porins. This decreases susceptibility to β‑lactams
and carbapenems, without altering target enzymes or producing β‑lactamases.
The mutations also slow nutrient uptake and reduce growth rate in antibiotic‑free
environments.

If antibiotic use remains high over time, what
evolutionary outcome is most likely?

Question

A Gram‑negative bacterial species
acquires mutations that reduce expression of outer‑membrane
porins. This decreases susceptibility to β‑lactams
and carbapenems, without altering target enzymes or producing β‑lactamases.
The mutations also slow nutrient uptake and reduce growth rate in antibiotic‑free
environments.

If antibiotic use remains high over time, what
evolutionary outcome is most likely?

Accepted Answer

Directional
selection favouring porin‑deficient strains

Answer

Purifying
selection eliminating porin mutations

Answer

Stabilizing
selection favouring intermediate porin expression

Answer

Diversifying
selection separating metabolic niches

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A Gram‑negative bacterial species acquires mutations that reduce expression of ...

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