[Molecular characterization of invasive Haemophilus influenzae strains isolated in Tunisia]

Étude de la résistance aux β-lactamines et des marqueurs moléculaires chez 157 souches d’Haemophilus influenzae isolées chez l’enfant à Tunis

The aim of this study was to precise the capsular type of Haemophilus influenzae , to determine its susceptibility to β-lactam agents, and to search for an eventual clonality between the clinical strains of the pathogen. Polymerase chain reaction was carried out to confirm the capsular type and to determine the β-lactamase type. Minimum inhibitory concentrations (MICs) of β-lactam agents for H. influenzae were determined by the agar dilution method on Haemophilus test medium, and the strains were analyzed by pulsed-field gel electrophoresis after SmaI restriction. Among 157 strains of H. influenzae studied, 12.1% was of serotype b. Sixty-seven strains (42.7%) were resistant to amoxicillin, among which 51 were resistant through production of TEM-type β-lactamase while 16 showed high MICs for amoxicillin, amoxicillin + clavulanic acid, and cefuroxim, which suggested a resistance by modification of penicillin-binding proteins. Among the latter strains, five were producing TEM-type β-lactamase. Cefotaxim, cefixim, and cefpodoxim had low MICs in all cases. The pulsed-field gel electrophoresis revealed 110 pulsotypes. All H. influenzae strains, including noncapsulated strains and serotype-b encapsulated strains, had a high level of heterogeneity, with diversity indices of respectively 0.67 and 0.94.