Guddu, a 5–year–old female was brought to the emergency with fever, headache and confusion. A provisional diagnosis of bacterial meningitis was made. The baby developed a severe allergic reaction to penicillin aroud six months back. She was admitted and intravenous antibiotics were started. Few days later her investigations revealed as: Hemoglobin – 6.0 g/L Erythrocyte count – 1.2 x 106/mm3 Platelets – 60000/mm3 Leukocyte count – 1500/mm3 Which of the following is the most likely drug responsible for the above findings ?