Substitutions in PBP3 confer resistance to both ampicillin and extended-spectrum cephalosporins in Haemophilus parainfluenzae as revealed by site-directed mutagenesis and gene recombinants.
J Antimicrob Chemother
; 72(9): 2544-2547, 2017 09 01.
Article
em En
| MEDLINE
| ID: mdl-28582518
ABSTRACT
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.
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Base de dados:
MEDLINE
Assunto principal:
Cefalosporinas
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Substituição de Aminoácidos
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Haemophilus parainfluenzae
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Proteínas de Ligação às Penicilinas
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Ampicilina
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Antibacterianos
Limite:
Humans
Idioma:
En
Ano de publicação:
2017
Tipo de documento:
Article