Complex sentence: Patients who have active bacteria are usually treated with a combination of medications; the primary antibiotic, isoniazid, is used in conjunction rifampin, ethambutol and pyrazinamide.
Split into simpler sentences: Patients who have active bacteria are usually treated with a combination of medications, at the same time with the main antibiotic, isoniazid. The main drugs used in conjunction with isoniazid are rifampin, ethambutol and pyrazinamide.