Background: The incidence of enterococci infection is on the rise. Treatment is ever more difficult due to the intrinsic resistance to many antimicrobial and their ability to acquire new resistance. The aim of this study was to: a) determine the antibiotic sensitivity of 80 enterococci strains isolated from blood in 1989-1993 and, b) detect the possible changes in the resistance patterns over this period.
Methods: Eighty enterococci strains isolated from blood cultures, since 1989 to 1993 were studied. Sixty-nine were Enterococcus faecalis and 11 Enterococcus faecium. The minimum inhibitory concentrations (MIC) of 11 antimicrobial was determined by the agar dilution method. The Mantel-Haenszel and Fisher tests were used for statistical analysis of the results.
Results: All the strains were sensitive to ampicillin and vancomycin. A high level of resistance (HLR) to gentamycin and streptomycin was observed in 18.7% and 23.7%, respectively of the strains. Fourteen strains (17.7%) presented HLR to both antibiotics. Approximately one third of the strains were resistant to the fluoroquinolones tested. Analysis of the results by year only demonstrated a significant lineal trend of resistance for ofloxacin (p = 0.014) and a significant difference between the years for ciprofloxacin (p = 0.017). Strains with an MIC > or = 16 mg/l of fluoroquinolones presented HLR to gentamycin (p < 0.001) and to all the aminoglucosides (p < 0.001).
Conclusions: The incidence of antibiotic resistance of enterococci isolated from blood in the authors hospital is generally low and, with the exception of the fluoroquinolones, did not demonstrate any significant differences during the period studied. Periodic updating and analysis of sensitivity results are required to monitor any changes which may occur over time.