Characterization of clinical isolates of beta-lactamase-negative, highly ampicillin-resistant Enterococcus faecalis

Area of Science:

• Microbiology
• Molecular Biology
• Antimicrobial Resistance

Background:

• Enterococcus faecalis is a significant cause of hospital-acquired infections.
• Ampicillin is a key antibiotic used to treat E. faecalis infections.
• Penicillin-binding proteins (PBPs) are essential targets for beta-lactam antibiotics like ampicillin.

Purpose of the Study:

• To investigate the penicillin-binding protein (PBP) profiles of ampicillin-resistant Enterococcus faecalis clinical isolates.
• To identify potential alterations in PBPs associated with high-level ampicillin resistance.

Main Methods:

• Analysis of penicillin-binding protein (PBP) profiles using techniques like SDS-PAGE.
• Determination of ampicillin Minimum Inhibitory Concentrations (MICs) for clinical isolates.
• Comparison of PBP expression and penicillin binding between resistant and susceptible strains.

Main Results:

• Two clinical isolates of E. faecalis exhibited high ampicillin MICs (32 and 64 µg/ml).
• Six distinct PBPs were detected in both isolates.
• An apparent increase in PBP 5 quantity and decreased penicillin binding for PBPs 1 and 6 were observed in the resistant isolates.

Conclusions:

• Alterations in penicillin-binding proteins (PBPs) are potentially linked to ampicillin resistance in Enterococcus faecalis.
• Specific changes, including increased PBP 5 and reduced binding of PBPs 1 and 6, may contribute to resistance mechanisms.
• Further research is warranted to elucidate the precise role of these PBP alterations in ampicillin resistance.