The inoculum effect of fosfomycin in tests with Enterococcus / 中华传染病杂志

ABSTRACT

Objective To investigate the inoculum effect of fosfomycin on enterococci,in comparison with penicillin,rifampin,vancomycin and teicoplanin.Methods A total of 91 strains of enterococci were obtained from the patients hospitalized in The First Affiliated Hospital of China Medical University from January 2010 to January 2012.There was no repeated strain.The 91 strains consisted of 44 Enterococcus faecalis and 47 Enterococcus faecium strains.Agar dilution method was used to measure the minimum inhibitory concentrations (MIC) of the five antibiotics against the 91 enterococci strains under standard low inoculation concentration (1 × 105 colony-forming units [cfu]/mL) and high inoculation concentration (1 × 107 cfu/mL).Results For all tested strains,MIC of fosfomycin fluctuated between 16-64 tμg/mL in high and low inoculated concentrations.Among the tested strains,both Enterococcus faecalis and Enterococcus faecium had the highest drug-sensitive rate (100.0％) and the lowest drugresistance rate (0) to fosfomycin.With the increase of the inoculation concentration,MIC of the five antibiotics increased less than 8 times,which indicated that there was no inoculation effect.Conclusion Fosfomycin shows high drug-sensitivity against enterococci without inoculum effect in vitro,and it is recommended for the treatment of enterococci-infected patients.