TURNOVER OF NONENCAPSULATED HAEMOPHILUS-INFLUENZAE IN THE NASOPHARYNGES OF OTITIS-PRONE CHILDREN

Restriction enzyme analysis of total genomic DNA was applied to study the epidemiology of nontypeable Haemophilus influenzae (NTHI) isolated from the nasopharynges of children with recurrent acute otitis media (AOM). The turnover of strains, as judged from genetic fingerprinting of a total of 213 H. influenzae isolates collected prospectively durin g a 2-year study period from 38 children under 3 years of age, was exa mined in relation to episodes of AOM as well as to courses of antibiot ic treatment. The children were selected if they had had at least one episode of AOM before 1 year of age and if more than two nasopharyngea l isolates of H. influenzae were recovered. The 213 H. influenzae isol ates (90% NTHI) recovered corresponded to 128 different DNA fingerprin ts. Fifty-eight percent of the fingerprints were observed only once, w hereas 42% appeared on two or more occasions in isolates from the same individual or in close relatives, i.e., brothers and sisters; Sixty-s even percent of these strains had a minimum colonization period of 2 m onths or less. Intermittent nasopharyngeal colonization periods longer than 5 months could be demonstrated for 13% of the strains. The prese nt data suggest that intermittent colonization is due to endogenous re infections. Genetically identical NTHI strains from unrelated individu als were never identified. As expected from the observation of a relat ively high proportion of persistent colonizations, no correlation was found bet ween episodes of AOM and the acquisition of new strains of N . influenzae, nor was any direct relation between antimicrobial therap y and the elimination of nasopharyngeal colonization, with a particula r strain of H. influenzae observed.