Biochemical differentiation of Haemophilus influenzae. Additional characterization of biotypes by carbohydrate fermentation patterns.

A total of 295 strains of H. influenzae was characterized by serotyping and biochemotyping following the scheme of Kilian. Biotype II was the biotype most frequently seen (41.4% of the strains). The strong correlation of serotype b with biotype I was confirmed. Carbohydrate degradation was evaluated as a possible aid for further characterization of biotypes. Differing results were obtained concerning the fermentation of fructose, maltose and xylose which were classified into five carbohydrate fermentation patterns A-E. To a certain degree the carbohydrate fermentation patterns of the strains could be associated with biotypes. No conclusion could be drawn, however, from carbohydrate fermentation patterns regarding sites of isolation and probable virulence of H. influenzae strains. The results of serotyping, biochemotyping according to Kilian and carbohydrate fermentation pattern analysis were correlated with clinical syndromes associated with isolation of the strains. Carbohydrate fermentation patterns permit a further differentiation of the serotype b/biotype I strains which can cause meningitis and other severe H. influenzae infections. A far more heterogeneous distribution of biochemical characteristics in strains isolated from the respiratory tract might facilitate epidemiological studies on respiratory diseases due to H. influenzae.