Molecular epidemiology of ampicillin-resistant non-beta-lactamase-producing Haemophilus influenzae

Abstract

Resistance to ampicillin without beta-lactamase production is not a frequent occurrence among Haemophilus influenzae strains. This kind of resistance is encountered in unencapsulated strains isolated from bronchial secretions and ear, nose, and throat specimens and is exceptional in H. influenzae type b. We studied 29 of these strains from various areas in France and 2 reference strains. Strains were compared by using ribotyping, arbitarily primed PCR with two primers, and pulsed-field gel electrophoresis. Each technique enabled the identification of 20 to 23 different patterns among the 31 strains. The combination of the different patterns for the strains obtained by the different techniques provided 27 distinct profiles. According to these results, it seems that the clonal propagation of these resistant strains does not occur.

FIG. 1

Patterns for AMP^r β− H. influenzae strains obtained by RT. The dendrogram and RT patterns of EcoRI-restricted H. influenzae DNA were analyzed with Taxotron software. Strains 1 to 31 are described in Table 1. S, strains; D, areas.

FIG. 2

Patterns for AMP^r β− H. influenzae strains obtained by AP-PCR with primer 217δ2. The dendrogram and AP-PCR profiles obtained with primer 217δ2 of H. influenzae were analyzed with Taxotron software. Strains 1 to 31 are described in Table 1. The Molecular Weight III marker was from Boehringer Mannheim. S, strains; D, areas.

FIG. 3

Patterns for AMP^r β− H. influenzae strains obtained by AP-PCR with primer RapIV. The dendrogram and AP-PCR profiles obtained with primer RapIV of H. influenzae were analyzed with Taxotron software. Strains 1 to 31 are described in Table 1. The Molecular Weight III marker was from Boehringer Mannheim. S, strains; D, areas.

FIG. 4

Patterns for AMP^r β− H. influenzae strains obtained by PFGE. The dendrogram and PFGE profiles of SmaI-digested DNA of H. influenzae were analyzed with Taxotron software. Strains 1 to 31 are described in Table 1. The bacteriophage lambda Ladder PFG Marker was obtained from Biolabs. S, strains; D, areas.