Since the current treatment is not working, your daughter may have an antibiotic-resistant bacterial strain or a different infection. Please do not start a new antibiotic without a doctor's guidance. You should take her to a physician immediately. They will likely order a stool culture test to identify the specific pathogen and prescribe an effective alternative antibiotic, such as Azithromycin or a cephalosporin. In the meantime, focus on preventing dehydration by giving her Oral Rehydration Salts (ORS) and plenty of fluids. Seek urgent medical care if she has a high fever, severe abdominal pain, or cannot keep fluids down.

For a suspected stomach infection with vomiting and diarrhea, the most critical step is preventing dehydration. Drink Oral Rehydration Salts (ORS) or electrolyte solutions in small, frequent sips. You can take an over-the-counter antiemetic (like Ondansetron) to control vomiting and probiotics to help restore gut health. Avoid anti-diarrheal medications (like loperamide) if you have a fever or bloody stools, as they can worsen infections. Please do not take antibiotics without a doctor's prescription. Stick to a bland diet, and seek immediate medical care if you cannot keep fluids down, experience severe abdominal pain, high fever, or notice blood in your stool.

Passing stools 3-4 times daily for a long time with black color is not typical simple Dysentery and needs proper evaluation, as black stools may suggest bleeding (like Melena). Avoid self-medication and get tests like stool exam and possibly endoscopy. Please consult a gastroenterologist soon, as long-term symptoms need proper diagnosis and treatment.