Activity of the French H-influenzae National Reference Center, 1996-1997:: Years of decline of type B.

During the years 1996 and 1997, a total of 1100 and 969 strains were collected respectively at the French H, influenzae National Reference Center. The results show an important decrease of encapsulated strains and of type b isolates. The place lost by type b is not occupied by any other capsular type. During these two years an important decrease of meningitis occurrence was also observed, Strains isolated from meningitis were non-typable in 50% of the cases, type f occured in two cases in adults and children and type e in one case in adult. These dramatic changes could be due to the impact of H, influenzae type b vaccine, In the same period and for all the strains, beta-lactamase production had increased and concerned 29,6% of the strains in 1996 and 34,8% in 1997. Beta-lactamase production concerned 40% of the strains isolated from otitis media. Ampicillin resistance without beta-lactamase production was detected in 0.9% of the strains studied in 1997 (non capsulated strains). Resistance to tetracycline (9,8%), and chloramphenicol (2%) was quite similar to the previous surveys; resistance to co-trimoxazole had increased and concerned 14,4% of the strains in 1997.