Efficacy of ampicillin plus arbekacin in experimental rabbit endocarditis caused by an Enterococcus faecalis strain...

Area of Science:

• Microbiology
• Infectious Diseases
• Pharmacology

Background:

• Enterococcus faecalis is a common cause of healthcare-associated infections, including endocarditis.
• High-level gentamicin resistance (HLGR) in E. faecalis, often mediated by the aac(6 ewer)-Ie-aph(2newer)-Ia gene, complicates treatment.
• Ampicillin is a standard treatment, but resistance mechanisms necessitate exploring alternative or combination therapies.

Purpose of the Study:

• To evaluate the in vivo efficacy of ampicillin in combination with arbekacin compared to ampicillin alone or ampicillin plus gentamicin.
• To assess treatment outcomes in a rabbit model of aortic-valve endocarditis caused by a specific ampicillin-susceptible, HLGR E. faecalis isolate (LC40).

Main Methods:

• A rabbit model of aortic-valve endocarditis was established using Enterococcus faecalis LC40.
• Bacterial vegetation counts were determined after treatment with ampicillin alone, ampicillin plus gentamicin, or ampicillin plus arbekacin.

Main Results:

• The combination of ampicillin plus arbekacin significantly reduced mean bacterial vegetation counts compared to ampicillin alone.
• Ampicillin plus arbekacin was also significantly more effective than ampicillin plus gentamicin in reducing bacterial vegetation.
• Enterococcus faecalis LC40 was identified as an ampicillin-susceptible isolate with high-level gentamicin resistance due to the aac(6 ewer)-Ie-aph(2newer)-Ia gene.

Conclusions:

• Ampicillin combined with arbekacin demonstrates superior efficacy over ampicillin alone and ampicillin plus gentamicin for treating experimental E. faecalis endocarditis.
• Arbekacin represents a promising therapeutic option in combination with ampicillin for HLGR Enterococcus faecalis infections.