567 SURVIVAL AND TRANSMISSION OF HAEMOPHILUS INFLUENZAE TYPE B (Hib) IN DAY CARE

Abstract

Hib is thought to be a fastidious organism. Transmission in institutional settings is assumed to be via large droplet respitory secretions. The role of environmental surfaces and fomites in transmission is unknown. Cultures were obtained from Hib carrier (Hib-C) children and their freshly handled fomites at three day care centers. Hib was recovered from 5/5 cultures of moist nasal secretions (NS), 1/5 cough plates held 10 inches from the mouth, but not from 27 cultures of saliva, hands, cribs and toys of Hib-C. Pooled NS from 3 Hib-C contained 1.6×10⁷ Hib CFU/ ml. Infected NS were smeared onto dry and premoistened washrags (WR) and Kleenex®. Survival of Hib was determined by growth in supplemented overnight BHI broth at intervals 0-5 hr UR and 0-18 hr Kleenex®. Hib in NS were recovered from dry WR for 3 hr, from moistened WR for 5 hr and Kleenex® for 18 hr. A pharyngeal Hib strain was diluted to 6×10⁶ CFU/ml in unsupplemented BHI broth and 50 μl were placed on moisten gauze (MG) and dry gauze (DG) and wax paper (WP). Colony counts were determined for 6-7 days. There was no drop in CFU in broth on gauze or WP until dried (0.5-3 hr). Thereafter dried Hib survived on MG at 10² CFU/ml for 3 days and was still recovered on day 6. Hib was recovered from DG and WP at 10² CFU/ml at seven days. NS of Hib-C contain high concentrations of Hib and support prolonged survival. Use of WR and Kleenex® for more than one child may contribute to transmission of Hib.

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