Diphtheroid prosthetic valve endocarditis. A study of clinical features and infecting organisms

Area of Science:

• Infectious Diseases
• Cardiology
• Microbiology

Background:

• Prosthetic valve endocarditis (PVE) is a serious complication following cardiac surgery.
• Diphtheroids, including CDC group JK, are increasingly recognized as pathogens in PVE.
• Early diagnosis and effective antimicrobial therapy are crucial for patient outcomes.

Purpose of the Study:

• To investigate the clinical characteristics of PVE caused by diphtheroids.
• To evaluate the in vitro antimicrobial susceptibility of diphtheroid isolates.
• To assess the efficacy of antibiotic combinations against these pathogens.

Main Methods:

• Retrospective review of 19 patients with PVE due to diphtheroids.
• Agar dilution and time-kill studies to determine minimal inhibitory concentrations (MICs) and bactericidal activity.
• Biochemical and physiologic characterization of isolated diphtheroid strains.
• Evaluation of antibiotic synergy using penicillin-gentamicin combinations.

Main Results:

• Infection occurred within 60 days of surgery in 63% of patients.
• Prosthetic valve dysfunction and annular infection were prevalent (74%).
• High susceptibility rates (88%) were observed for gentamicin, amikacin, streptomycin, erythromycin, and tetracycline; all strains were susceptible to vancomycin.
• Vancomycin and gentamicin demonstrated potent bactericidal activity.
• Penicillin-gentamicin combinations showed synergy against gentamicin-susceptible strains.

Conclusions:

• Diphtheroid PVE presents with early onset and significant prosthetic valve involvement.
• Vancomycin and gentamicin are effective bactericidal agents.
• Combination therapy with penicillin and gentamicin may be beneficial for susceptible strains, but not for gentamicin-resistant strains.
• Standardized susceptibility testing methods are needed for accurate diagnosis and treatment guidance.