Answer
The patient may have nalidixic acid resistant bacteria, due to which her infection did not heal. However, when she used sulfonamide, her infection healed as the bacteria was not reistant to sulfonamide.
Work Step by Step
The patient may have nalidixic acid resistant bacteria, due to which her infection did not heal. However, when she used sulfonamide, her infection healed as the bacteria was not reistant to sulfonamide.