CARRIAGE OF MULTIPLE RIBOTYPES OF NONENCAPSULATED HAEMOPHILUS-INFLUENZAE IN ABORIGINAL INFANTS WITH OTITIS-MEDIA

Ribotyping with the restriction enzyme XbaI was used to study the dyna mics of carriage of non-encapsulated Hnemophilus influenzae (NCHi) in Aboriginal infants at risk of otitis media. Carriage rates of NCHi in the infants in the community were very high; the median age for detect ion was 50 days and colonization was virtually 100% by 120 days of age and persisted at a high level throughout the first year of life [1]. Eighteen different ribotypes of NCHi were identified from 34 positive swabs taken from 3 infants over a period of 9 months. The same ribotyp es were recovered for up to 3 months from consecutive swabs of individ ual infants, and 12 of 27 swabs (44.4%) yielded two ribotypes from fou r colonies typed. Statistical analysis suggested that most swabs would have been positive for two ribotypes if enough colonies had been type d although the second most frequent ribotype was detected on average i n only 13% of strains. Early colonization and carriage of multiple rib otypes of NCHi may help to explain the chronicity of carriage and thus the persistence of otitis media in Aboriginal infants.