Evaluation of mutations in penicillin binding protein-3 gene of non-typeable Haemophilus influenzae isolated from the nasopharynx of children with acute otitis media

Conclusion Younger children tend to harbor more resistant strains because they are exposed to these pathogens more often through contacts with siblings or attendance at day-care centers and are frequently treated with antibiotics. The high prevalence of BLNAR strains should be taken into account in the treatment of AOM in young children. Objective Non-β-lactamase-producing ampicillin-resistant (BLNAR) strains with mutations in penicillin-binding protein (PBP) genes of Haemophilus influenzae have been prevalent recently among younger children. Material and methods We investigated mutations in the ftsI gene encoding PBP-3 of H. influenzae isolated from the nasopharynx of children with acute otitis media (AOM) using polymerase chain reaction (PCR). Results Strains containing the bla gene (β-lactamase-producing ampicillin-resistant) were identified in 4.7% of cases. Strains with mutations in the ftsI gene (BLNAR) were identified in 23.3% of cases. Strains without mutations in the ftsI gene and that did not contain the bla gene (non-β-lactamase-producing ampicillin-susceptible) were identified in 70.7% of cases. Strains with both expression of the bla gene and mutations in the ftsI gene (β-lactamase-producing amoxicillin–clavulanate-resistant) were identified in 1.3% of cases. The MICs of ampicillin against the strains evaluated in this study were 0.5–2.0 μg/ml. Cefditoren-pivoxil had the lowest MIC₉₀ against the strains (0.06 μg/ml). Strains with mutations in the ftsI gene (BLNAR) were broadly identified among young children.