Multiply high-level-aminoglycoside-resistant enterococci isolated from patients in a university hospital

Enterococci isolated from different body sites were tested for high-level gentamicin resistance. A total of 259 enterococcal isolates were screened for resistance (MIC, greater than 2,000 micrograms/ml) by a broth-tube method. Thirty-nine (15.1%) were found to exhibit resistance and were confirmed by agar screening (1,000 micrograms/ml) and agar dilution MIC determinations. The majority of isolates also showed high-level resistance to kanamycin and streptomycin. The remaining isolates showed high-level resistance to gentamicin and kanamycin but not streptomycin. Synergy testing of several isolates confirmed the correlation between lack of synergy and high-level resistance. A retrospective clinical review was performed. Most patients had a source of definite or likely infection (79%). Serious infections such as endocarditis or meningitis were not observed during the course of this study. Retrospective clinical data suggest that in cases not involving endocarditis or meningitis, neither infection refractory to therapy nor relapse of infection is a common sequela of infection with gentamicin-resistant enterococci in hospitalized patients.