Increasing ampicillin-resistance rates in Hemophilus influenzae meningitis

G. R. Istre, J. S. Conner, M. P. Glode and R. S. Hopkins

We studied the epidemiology of reported Hemophilus influenzae meningitis in Colorado for the years 1977 through 1981. Of 340 culture-confirmed cases, 94% occurred in children less than 5 years old. A marked seasonal variation was present, with peaks in late fall-early winter and late spring. The percentage of H influenzae isolates resistant to ampicillin increased from 4.2% in 1977 to 31.3% in 1981. The incidence of reported disease in children younger than 5 years of age increased from 26 per 100,000 population in 1977 to 39 per 100,000 population in 1981, The overall case fatality rate was 5.2%; mortality was somewhat higher for persons with ampicillin-resistant infections (9.4%) than for those with ampicillin-sensitive infections (4.3%). Our results agree with previous reports of an increasing rate of ampicillin resistance in H influenzae meningitis and indicate a possible increasing incidence of this disease in Colorado.