All of the following are true regarding Haemophilus influenzae except: (A) It can be a part of the normal flora in some persons, (B) The serotyping is based on the bacterial outer membrane proteins, (C) It requires Haemin and NAD for growth in culture medium, (D) Type b is responsible for invasive disease
Answer is B. (B) The serotyping is based on the bacterial outer membrane proteins# Characteristics of Hemophilus influenzae: Hemophilus is a pleomorphic gram negative bacilli Hemophilus influenzae describes some of its properties Hemophilus means blood loving. This organism requires a blood containing medium for growth. Factor X and Factor V present in blood are essential for its growth (factor X acts physiologically as haemin and factor V is nicotinamide nucleotide) One important features of H. influenzae is that it does not grow properly on blood agar, because factor V is not available in blood agar as it is located inside red blood cells but when agar is heated to convert it into chocolate agar the factor V is released from R.B.C.'s> Hence H. influenzae grows better on chocolate agar> Antigenic structure: Encapsulated H. influenzae contains polysaccharide capsule. This polysaccharide capsule confers virulence Of these types of H. influenzae type b is commonly associated with invasive H. influenzae diseases such as Meningitis; Epiglottitis; Septic arthritis> Non capsulated strains of H. influenzae can colonize the upper respiratory tract of children and adults.> They lack the virulent invasiveness of encapsulated bacteria and can only cause local infection.