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J Antimicrob Chemother ; 72(9): 2544-2547, 2017 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-28582518

RESUMO

Objectives: To determine the association of amino acid substitutions in PBP3 with ß-lactam susceptibility in Haemophilus parainfluenzae. Methods: Single and multiple amino acid mutations at positions 385, 511 and 526 were introduced into PBP3 of a ß-lactam-susceptible H. parainfluenzae strain using site-directed mutagenesis. Recombinants were also generated using PCR-amplified ftsI from clinical strains encoding multiple amino acid substitutions. MICs of ampicillin, cefuroxime, cefotaxime and ceftriaxone were determined using Etest®. Results: Transformation of a susceptible strain with ftsI from clinical strains encoding four substitutions in the transpeptidase region of PBP3 conferred resistance to ampicillin, but not to cephalosporins. Introduction of ftsI from a clinical strain encoding eight substitutions conferred resistance to ampicillin, cefotaxime and ceftriaxone. MICs for recombinants were lower than those for the donor strains. Using site-directed mutagenesis, no single substitution conferred resistance to the tested ß-lactams, although V511A increased the MIC of cefuroxime to the intermediate category for intravenous administration. Recombinants encoding N526K/H/S in combination with V511A were resistant to ampicillin. Substitution S385T increased the MICs of third-generation cephalosporins if V511A was also present. Conclusions: Substitutions in PBP3 are sufficient to confer resistance to both ampicillin and third-generation cephalosporins in H. parainfluenzae. A combination of substitutions at positions Val-511 and Asn-526 confers resistance to ampicillin. Resistance to third-generation cephalosporins probably requires more than four substitutions in PBP3.


Assuntos
Substituição de Aminoácidos , Ampicilina/farmacologia , Antibacterianos/farmacologia , Cefalosporinas/farmacologia , Haemophilus parainfluenzae/efeitos dos fármacos , Haemophilus parainfluenzae/genética , Proteínas de Ligação às Penicilinas/genética , Farmacorresistência Bacteriana Múltipla/genética , Infecções por Haemophilus/microbiologia , Humanos , Testes de Sensibilidade Microbiana , Mutagênese Sítio-Dirigida , Recombinação Genética
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