Biotypes of Haemophilus influenzae that are associated with noninvasive infections.

In this study, we examined the biotypes of Haemophilus influenzae strains associated with noninvasive infections in hospitalized patients. Over an 18-month period, a total of 388 strains were isolated from patients of various ages (neonates to the elderly), and the biotypes of the strains were determined. Strains of biotype II accounted for 48% of the isolates; this was followed by strains of biotypes III and I (26 and 16%, respectively). The remaining 10% of the isolates were made up of strains of biotypes IV, V, VI, and VII. A total of 6% of strains were capsulated. The distribution of biotypes in specimens from the respiratory tract and associated sites was comparable to that obtained in similar investigations, but examination of isolates from neonatal and genital specimens did not support the concept that H. influenzae biotype IV is a major urogenital pathogen. Conflicting results regarding the incidence of certain biotypes in specimens, particularly those from the urogenital tract, may be due to the selection of different subpopulations of patients. Data relating to the specimens were used to evaluate the association between biotype and clinical diagnosis, the presence of other potential bacterial pathogens in the specimens, and the presence of viruses in the specimens. None of the differences in the distribution of biotypes which were examined was statistically significant.