Penicillin-netilmicin synergism against Streptococcus faecalis

Area of Science:

• Microbiology
• Pharmacology
• Infectious Diseases

Background:

• Enterococcal endocarditis is a serious infection.
• Aminoglycoside antibiotics are often used in combination therapy.
• Netilmicin is an aminoglycoside antibiotic with potential therapeutic applications.

Purpose of the Study:

• To evaluate the in vitro synergy of penicillin plus netilmicin against Streptococcus faecalis.
• To compare the efficacy of penicillin plus netilmicin with penicillin plus gentamicin in a rabbit model of enterococcal endocarditis.

Main Methods:

• In vitro susceptibility testing of 28 Streptococcus faecalis strains against penicillin and netilmicin.
• Experimental enterococcal endocarditis induced in 67 rabbits using streptomycin-susceptible or -resistant strains of S. faecalis.
• Treatment with penicillin plus netilmicin or penicillin plus gentamicin, with bacterial titers assessed in vegetations.

Main Results:

• Penicillin plus netilmicin demonstrated synergistic activity in vitro and was comparable to penicillin plus gentamicin in reducing bacterial titers in rabbit endocarditis models.
• After 10 days of therapy, penicillin plus netilmicin achieved lower mean valve titers than penicillin plus gentamicin for both streptomycin-susceptible and -resistant strains.

Conclusions:

• Penicillin plus netilmicin is effective in treating experimental enterococcal endocarditis.
• Netilmicin may be a useful alternative to gentamicin in combination therapy for enterococcal endocarditis, pending further toxicity studies.