Clonal spread of an invasive strain of Haemophilus influenzae type b amongnursery contacts accompanied by a high carriage rate of nondisease-associated strains

Haemophilus influenza carriage was examined in unvaccinated nursery contact s of a patient with fi, influenzae type b (Hib) meningitis and isolates wer e typed by pulsed-field gel electrophoresis (PFGE), Nasopharyngeal isolates were classified into eight PFGE patterns. Seven Nib carriers were found am ong 15 nursery contacts. The isolates from the carriers showed a PFGE patte rn identical to that of the meningitis strain. The carrier rate of non-dise ase-associated strains was also high (47%, 7 of 15), This study suggests th at the clonal spread of invasive (serotype b) H, influenzae strains is acco mpanied by a high carriage rate of non-disease-associated strains.