Addition of isovitalex in chocolate agar for the isolation of Haemophilus influenzae

The reason for lack of data on burden of Haemophilus influenzae type b (Hib) in developing countries was mainly failure of detection of this fastidious organism in laboratories. Use of isovitalex (IVX) was suggested as an essential supplement for growing this organism. This study was carried out to investigate the impact of IVX supplementation to chocolate agar for detection of Hib.

Chocolate agar with and without supplementation of IVX was prepared. Clinical samples as well as reference strains of Hib were simultaneously cultured on both the media.

H. influenzae isolates (N=194) were simultaneously grown on chocolate agar (CA) with and without isovitalex (IVX). Average colony size of H. influenzae on CA with IVX (CA-IVX) was larger only by 0.10 cm (range 0.05 to 0.16 cm) compared to CA alone. Addition of IVX to CA increased the cost of media by 2.1-fold.

Isovitalex is not essential for the isolation and growth of H. influenzae almost halving the cost.