A study on Haemophilus influenzae type b growth rate and capsule production in different media

In the present study, seven isolates of Haemophilus influenzae type b were cultured in four different media to compare growth rate and capsule production. Four liquid media namely brain heart infusion broth (BHI), trypticase soy broth (TSB), Mueller Hinton Broth (MHB) and Gonococci broth (GC) with added supplements (1% hemoglobin, 1% Isovitalex) were used. The growth was measured by colony counting (CFU/ml) using serial dilution. Four of the isolates showed the highest growth rate with the average of 1013 CFU/ml on BHI broth while TSB had the second highest growth of more than 1010 CFU/ml in an 18-hour culture at 37 ºC culture. In the next step, the amount of capsular polysaccharide (CPS-b) antigen which is made of Polyribosyl ribitol phosphate (PRP) was assessed all isolates by two methods: modified Indirect Sandwich Enzyme-linked immunosorbent assay (ELISA) and Bial method to select the isolate producing the highest amount of PRP. The antisera used in sandwich ELISA were prepared by immunization of Rabbit and Rat. The maximal amount of PRP was produced by isolate Hib (5s) with the amount of 321 mg/lit.