Three Hemophilus Species

Over a 16-month period Hemophilus species were isolated from 16 patients with serious infections. The infecting species was H parainfluenzae in ten cases, H influenzae in five, and H parahemolyticus in one. Seventy-five percent of the infections occurred in children between the ages of 6 months and 4 years; the remaining 25% occurred in older patients who had associated conditions compromising host defense mechanisms. Antibiotic therapy was successful in all but one case. In a supplementary survey to determine the frequency of various Hemophilus species in the throat flora of normal children, 11% had H influenzae , 12% had H parainfluenzae , and 20% had H parahemolyticus ; these isolation rates were not significantly different from those in throat cultures from another group of children of comparable age with upper-respiratory tract disease.