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[Comparison of susceptibilities for fosfomycin determined by various methods in clinical isolates in 2003 -2004]
Hideaki Muramatsu1, Jinko Ishikawa, Osanori Nagura
1Hamamatsu University School of Medicine.
Abstract:
Antimicrobial susceptibilities for fosfomycin (FOM), cephalexin, cefpodoxime, cefdinir, cefditren, ampicillin, sulbactam/ampicillin, imipenem (IPM), panipenem, meropenem (MEPM), biapenem, levofloxacin (LVFX), gatifloxacin, pazufloxacin, prulifloxacin and sulfamethoxazole/trimethoprim were determined by an agar dilution method using Mueller-Hinton agar (MHA) in Escherichia coli, Klebsiella spp., Serratia marcescens, Citrobacter spp., Enterobacter spp. and Proteus mirabilis, which were isolated from patients in 2003-2004. Those for FOM were determined by the agar dilution methods using MHA containing glucose-6-phosphate (G6P) under aerobic conditions, MHA under anaerobic conditions and nutrient agar under aerobic conditions. Those for FOM, LVFX, IPM and MEPM were also determined by an Etest method. The results by the agar dilution method showed that carbapenems had good antibacterial activities in all isolates, whereas MIC ranges for other antimicrobials were broad. Our results showed that the agar dilution method for FOM using MHA containing G6P under aerobic conditions provided reliable MICs in E. coli, which agreed with data previously reported. The results by the agar dilution method for LVFX, IPM and MEPM showed the high rate of agreement compared with those by the Etest method. In E. coli, the results for FOM by the agar dilution method using MHA containing G6P showed the high rate of agreement compared with the Etest results, although the rate was affected by bacterial species and culture conditions in various ways.
Insights
Antimicrobial testing revealed carbapenems show strong activity against common Gram-negative bacteria. Fosfomycin susceptibility testing using Mueller-Hinton agar with glucose-6-phosphate is reliable for E. coli.
Area of Science:
- Clinical Microbiology
- Antimicrobial Resistance
- Bacterial Pathogenesis
Background:
- Gram-negative bacterial infections pose a significant public health threat.
- Monitoring antimicrobial resistance patterns is crucial for effective treatment.
- Carbapenems and fosfomycin are important antibiotics for treating Gram-negative infections.
Purpose of the Study:
- To evaluate the antimicrobial susceptibilities of common Gram-negative pathogens.
- To compare different methods for fosfomycin susceptibility testing.
- To assess the reliability of agar dilution and Etest methods.
Main Methods:
- Agar dilution method used to determine Minimum Inhibitory Concentrations (MICs) for various antimicrobials against clinical isolates of Escherichia coli, Klebsiella spp., Serratia marcescens, Citrobacter spp., Enterobacter spp., and Proteus mirabilis.
- Specific conditions for fosfomycin (FOM) susceptibility testing included Mueller-Hinton agar (MHA) with glucose-6-phosphate (G6P) aerobically, MHA anaerobically, and nutrient agar aerobically.
- Etest method was employed to compare results for FOM, levofloxacin (LVFX), imipenem (IPM), and meropenem (MEPM).
Main Results:
- Carbapenems (imipenem, panipenem, meropenem, biapenem) demonstrated excellent activity against all tested Gram-negative isolates.
- MIC ranges for other tested antimicrobials were broad, indicating variable susceptibility.
- Agar dilution method for FOM using MHA with G6P under aerobic conditions yielded reliable MICs for E. coli, consistent with prior reports.
- High agreement was observed between agar dilution and Etest methods for FOM, LVFX, IPM, and MEPM.
- Fosfomycin testing agreement in E. coli was high, though influenced by bacterial species and culture conditions.
Conclusions:
- Carbapenems remain highly effective against the studied Gram-negative bacteria.
- The agar dilution method with MHA containing G6P under aerobic conditions is a reliable method for determining fosfomycin susceptibility in E. coli.
- Methodological variations can impact antimicrobial susceptibility testing results, highlighting the need for standardized protocols.
