Observations on Bacillus (Haemophilus) influenzae with Special Reference to Morphology and Colonial Characters

Abstract

1. Several strains of the influenza bacillus were grown under varying conditions for many months in order to ascertain whether morphology and colonial appearances could be permanently modified.2. It was found that a modification in morphology occurred in all the strains studied.3. Typical coccobacillary forms were changed to atypical long-curved forms.4. The reverse change from atypical was also observed but was not so frequent, nor, when it occurred, was it so constant.5. The change took place most readily after growth in a flask of Fildes' broth for several weeks or months at 37° C.6. There was found to be a definite association between morphology and colonial form. The typical strains produced smooth colonies, while the atypical gave rough colonies, or colonies very much smaller than those produced by the typical.7. When the change in morphology took place the change in colonial form occurred at the same time.8. The biochemical characters remained on the whole unchanged.9. One hundred and forty strains were examined for their fermentation reactions. The sugars most frequently fermented were dextrose, maltose and sucrose.10. The atypicals were more active fermenters than the typicals.11. 63·9 per cent. of the typicals, and 18 per cent. of the atypicals, gave a positive indol reaction.12. Although the ability to grow on X or V alone affords an important differential criterion within this group, great care is necessary in interpreting the results obtained, especially in the case of those strains which grow on V in the absence of X. Different yeast preparations may give very different results in this respect.13. All the strains tested were non-haemolytic.