Abstract
We describe imipenem-resistant and imipenem-susceptible clinical isolates of Clostridium difficile ribotype 017 in Portugal. All ribotype 017 isolates carried an extra penicillin-binding protein gene, pbp5, and the imipenem-resistant isolates had additional substitutions near the transpeptidase active sites of pbp1 and pbp3. These clones could disseminate and contribute to imipenem resistance.
Highlights
We describe imipenem-resistant and imipenem-susceptible clinical isolates of Clostridium difficile ribotype 017 in Portugal
Imipenem resistance in C. difficile RT017 probably involves the acquisition of mutations in both pbp1 and pbp3 that lead to amino acid substitutions close to the functional motifs of their transpeptidase domains
Considering that the presence of an additional penicillin-binding proteins (PBPs) (PBP5) is a characteristic of RT017 strains, we suggest that PBP5 facilitates the expression of imipenem resistance through acquisition of mutations in pbp1 and pbp3
Summary
Imipenem resistance in C. difficile RT017 probably involves the acquisition of mutations in both pbp and pbp that lead to amino acid substitutions close to the functional motifs of their transpeptidase domains. These substitutions might decrease the affinity of PBP1 and PBP3 for imipenem, enabling peptidoglycan synthesis in the presence of the antimicrobial drug. Considering that the presence of an additional PBP (PBP5) is a characteristic of RT017 strains, we suggest that PBP5 facilitates the expression of imipenem resistance through acquisition of mutations in pbp and pbp. In strains of other ribotypes lacking PBP5, such as the RT014 and RT477 isolates described, mutations in pbp might only lead to
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