Penicillin-binding proteins involved in high-level piperacillin resistance in Veillonella spp

Abstract

Objectives: To investigate high-level piperacillin resistance in Veillonella spp. in the absence of β-lactamase activity. Methods: Penicillin-binding protein (PBP) competition studies were conducted in Veillonella strains, with piperacillin MICs ranging from 0.5 to >128 mg/L and ampicillin MICs from 0.125 to 4 mg/L. Whole cell lysates were pre-incubated with piperacillin or ampicillin and post-labelled with [3H]benzylpenicillin. Results: PBP competition studies showed that the PBP with greatest affinity for penicillin and ampicillin had a molecular weight of ∼66 kDa, and exhibited reduced binding of piperacillin in resistant strains. Conclusions: This unusual focusing of different penicillins on one PBP may be the cause of selective mutants resulting from piperacillin MICs > 128 mg/L. In the absence of β-lactamases, alterations in penicillin-binding were seen to be major contributors to high-level piperacillin resistance development.