Haemophilus influenzae carriage in children attending French day care centers: a molecular epidemiological study

Abstract

The nasopharyngeal Haemophilus influenzae flora of healthy children under the age of 3 years attending day care centers in three distinct French geographic areas was analyzed by sampling during two periods, spring 1999 (May and June) and fall 1999 (November and December). The average carrier rate among 1,683 children was 40.9%. The prevalence of capsulated H. influenzae carriers was 0.4% for type f and 0.6% for type e. No type b strains were found among these children, of whom 98.5% had received one or more doses of anti-Haemophilus b vaccine. Among the strains, 44.5% were TEM-type beta-lactamase producers and nine (1.3%) were beta-lactamase-negative ampicillin-resistant strains. Pulsed-field gel electrophoresis restriction patterns showed a large diversity with 366 SmaI patterns from 663 strains. Among the strains isolated during a given period, 33% were isolated simultaneously in more than one area. In each area, depending on the sampling period, 68 to 72% of the strains had new pulsotypes and persistence of 28 to 32% of the strains was noted. For the 297 beta-lactamase-producing strains, 194 patterns were found. The genomic diversity of these strains was comparable to that of the whole set of strains and does not suggest a clonal diffusion. Among the beta-lactamase-producing strains isolated in November and December, depending on the area, 66 to 73% had new pulsotypes with persistence of only 27 to 33% of the strains. In any given geographic area, colonization by H. influenzae appears to be a dynamic process involving a high degree of genomic heterogeneity among the noncapsulated colonizing strains.

FIG. 1.

PFGE profiles of SmaI-restricted H. influenzae DNA of strains isolated from children attending DCCs in the Doubs area during the November-to-December period. Lanes (left to right): 1, H. influenzae ATCC 10211; 2, child from DCC 04; 3 to 8, children from DCC 05; 9, child from DCC 06; 10, lambda ladder; 11, child from DCC 07; 12 to 17, children from DCC 08; 18 and 19, children from DCC 09; 20, lambda ladder; 21 to 25, children from DCC 09; 26, child from DCC 08; 27 and 28, children from DCC 06; 29, uninterpretable; 30, H. influenzae ATCC 10211.

FIG. 2.

PFGE analysis dendrogram showing the genetic relationship among strains of H. influenzae isolated from children attending DCCs in three different geographic areas of France during the period from November to December 1999. For each area the number indicates the number of strains in the pattern; −, no strain in the pattern. The dendrogram is shown in four portions, in order from left to right, with the bottom of one portion corresponding to the top of the next.

FIG. 2.

PFGE analysis dendrogram showing the genetic relationship among strains of H. influenzae isolated from children attending DCCs in three different geographic areas of France during the period from November to December 1999. For each area the number indicates the number of strains in the pattern; −, no strain in the pattern. The dendrogram is shown in four portions, in order from left to right, with the bottom of one portion corresponding to the top of the next.

FIG. 2.

PFGE analysis dendrogram showing the genetic relationship among strains of H. influenzae isolated from children attending DCCs in three different geographic areas of France during the period from November to December 1999. For each area the number indicates the number of strains in the pattern; −, no strain in the pattern. The dendrogram is shown in four portions, in order from left to right, with the bottom of one portion corresponding to the top of the next.

FIG. 2.

PFGE analysis dendrogram showing the genetic relationship among strains of H. influenzae isolated from children attending DCCs in three different geographic areas of France during the period from November to December 1999. For each area the number indicates the number of strains in the pattern; −, no strain in the pattern. The dendrogram is shown in four portions, in order from left to right, with the bottom of one portion corresponding to the top of the next.

FIG. 3.

PFGE analysis dendrogram showing the genotypic relationship among strains of H. influenzae isolated from children attending DCCs in the Alpes Maritimes area during the two study periods. For each period the number indicates the number of strains in the pattern; −, no strain in the pattern. The dendrogram is shown in three portions, in order from left to right, with the bottom of one portion corresponding to the top of the next.

FIG. 3.

PFGE analysis dendrogram showing the genotypic relationship among strains of H. influenzae isolated from children attending DCCs in the Alpes Maritimes area during the two study periods. For each period the number indicates the number of strains in the pattern; −, no strain in the pattern. The dendrogram is shown in three portions, in order from left to right, with the bottom of one portion corresponding to the top of the next.

FIG. 3.

PFGE analysis dendrogram showing the genotypic relationship among strains of H. influenzae isolated from children attending DCCs in the Alpes Maritimes area during the two study periods. For each period the number indicates the number of strains in the pattern; −, no strain in the pattern. The dendrogram is shown in three portions, in order from left to right, with the bottom of one portion corresponding to the top of the next.