ITERATIVE COLONIZATION BY HAEMOPHILUS INFLUENZAE IN HEALTHY CHILDREN LIVING IN AN ORPHANAGE

J. Raymond, L. Armand-Lefevre, F. Moulin, H. Dabernat, A. Commeau, P. Berche, D. Gendrel

Service Microbiologie., Hôpital Purpan,Toulouse,France., Hôpital Necker-Enfants Malades, Paris,France

Background: To study colonization and transmission of Haemophilus influenzae (Hi)on a cohort of healthy children under age of 2 years living in an orphanage.

Methods: Fifty-three children, aged 0 to 24 months, were followed over one year. All children more than 2 months were vaccinated against Hi serotype b. Nasopharyngeal cultures were collected monthly, or every 2 weeks in children under 6 months of age. Antibiotic susceptibility, serotyping, biotyping and genotyping (pulsed-field gel electrophoresis, PFGE) were performed for each isolate. As control, 39 Hi isolates fro various origins were used.

Results: Among the 111 isolates cultured from 43 of children (81%), 55.9% produced a ß-lactamase. Most isolates belonged to biotype II (62.2%), 4 strains (3.6%) to serotype f and none were serotype b. A complete concordance was found between biotype, serotype, pulsotype and antimicrobial susceptibility. In contrast to the high genetic heterogeneity of the 39 control isolates (37 pulsotypes), most isolates (82%) from the cohort belonged to only 5 pulsotypes. Three clones rapidly spread in the community and were then eliminated. The two others diffused in a more endemic manner. In younger children, the mean age of primary colonization was 2 months and the mean duration of carriage about 1.4 months for a given isolate. Each child was colonized by about 3 different strains. Reacquisition of t same pulsotype occured in 5 children.

Conclusion: In children living in this closed community, there is an early and sequential colonization by a low number of Hi clones rapidly spreading from child-to-child. The efficacy of anti-Hi vaccination is confirmed by the absence of carriage of Hi serotype b