Thanks for your query.
As your mother is having loose motion
due to gastroenteritis
. First she was put on blind therapy of antibiotics used in gastroenteritis, But when stool culture and sensitivity is done then it becomes easier for doctor to know what drug is sensitive for that particular bacteria. So ciprofloxcin would be more appropriate. It may take more than a week to eradicate infection so continue medication and fluid replacement.
Hope it helps.