Penicillin-binding protein 5 as an inhibitory target of cefozopran in Enterococcus faecalis

Area of Science:

• Microbiology
• Pharmacology
• Biochemistry

Background:

• Penicillin-binding proteins (PBPs) are crucial targets for beta-lactam antibiotics.
• Enterococcus faecalis is a significant opportunistic pathogen.
• Understanding antibiotic-PBP interactions is key to developing new antimicrobial strategies.

Purpose of the Study:

• To investigate the binding affinity of cefozopran to penicillin-binding protein 5 (PBP 5) in Enterococcus faecalis TN2OO5.
• To correlate cefozopran's PBP binding with its antimicrobial activity (Minimum Inhibitory Concentration - MIC).
• To compare cefozopran's PBP binding profile with other beta-lactam antibiotics.

Main Methods:

• Radioligand binding assay using [14C]benzylpenicillin to quantify PBP 5 inhibition by cefozopran.
• Determination of cefozopran's MIC against Enterococcus faecalis TN2OO5.
• Assessment of binding affinities of ceftazidime, cefmenoxime, ampicillin, benzylpenicillin, and imipenem to various PBPs.

Main Results:

• Cefozopran inhibited PBP 5 binding by 50% at 11 mg/L, with an MIC of 12.5 mg/L.
• Ceftazidime and cefmenoxime showed no significant affinity for PBP 5 at 100 mg/L.
• Ampicillin, benzylpenicillin, and imipenem exhibited higher affinity for PBPs 3/4 and PBP 5, with lower MICs than cefozopran.

Conclusions:

• Cefozopran's antimicrobial activity against Enterococcus faecalis TN2OO5 is likely mediated by its binding to PBP 5.
• The study highlights the specific PBP targeting mechanism of cefozopran.
• No correlation was observed between MICs and affinity for PBP 1, 2, or 6, suggesting PBP 5 is the primary target.