A 2 years old child is brought to the emergency with history of fever and vomiting. On examination he has neck rigidity. The CSF examination shows polymorphs more that 2000/m1 protein 100 mg/dl and glucose 10mg/d1. The Gram stain shows the presence of Gram negative coccobacilli. The culture shows growth of bacteria only on chocolate agar and not on blood agar. The caustive agent is ?

Ans. is 'b' i.e., Haemophilus influenzae . The impoant clues in this question are ? The organism is gram negative coccobacilli. It grows only on chocolate agar and not on blood agar. Causing meningitis in children. . Haemophilus influenzae : - Gram negative Coccobacilli - Can not grow in blood agar because utilization of V factor (NAD or NADP) is limited by the presence of serum NADase. - Grows well on chocolate agar (blood agar which is heated up to 70-80degC) because, on heating extra X and V factors are liberated from the lysed red cells. - Is a common cause of meningitis in children. About other options - N. Meningitis . It occur as diplococci (not coccobacilli) . It can grow on blood agar. - Legionella pneumophilia . Does not cause meningitis. - Bramanhella catarrhalis . It occur as diplococci (not coccobacilli) . It can grow on blood agar.