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In vitro activity of cefpirome (HR 810) against enterococci and staphylococci
E Piacentini1, G Amalfitano, M Ligozzi
1Institute of Microbiology, University of Verona, Italy.
Abstract:
The inhibitory activity of cefpirome (HR 810), a new cephalosporin derivative for parenteral use, was tested by agar dilution methods against Enterococcus faecalis (100 strains), Staphylococcus aureus (40 strains) and coagulase-negative staphylococcal species (60 strains) in comparison with other beta-lactam antibiotics. For E. faecalis, the cefpirome minimum inhibitory concentration (MIC) range was 2-128 micrograms/ml, with an MIC50 of 8 micrograms/ml, and an MIC90 of 64 micrograms/ml. The optimal bactericidal activity against strains with MICs of < or = 8 micrograms/ml occurred at 2-4 times the MIC, and the reduction in the initial inoculum was 99.9-99.7% after 24 h incubation at these concentrations. Mec gene-negative staphylococci (both S. aureus and coagulase-negative species) had cefpirome MICs of 0.25-2 micrograms/ml (MIC50 0.5 microgram/ml, MIC90 1 microgram/ml). Mec gene-positive strains had MICs of 0.5-128 micrograms/ml (MIC50 2 micrograms/ml, MIC90 32 micrograms/ml). Strains with borderline resistance to oxacillin which did not harbor the mec gene and which were susceptible to cefpirome maintained their susceptibility even when high-density inocula were used and after several passages in media containing the antibiotic. These studies present some potential advantages of cefpirome over other cephalosporins in the inhibitory activity against Gram-positive cocci.
Insights
Cefpirome demonstrates potent inhibitory and bactericidal activity against Gram-positive cocci, including Enterococcus faecalis and Staphylococcus aureus. This new cephalosporin shows promise, potentially offering advantages over existing treatments for Gram-positive bacterial infections.
Area of Science:
- Microbiology
- Pharmacology
- Infectious Diseases
Background:
- Gram-positive cocci, such as Enterococcus faecalis and Staphylococcus aureus, are significant pathogens.
- Beta-lactam antibiotics, including cephalosporins, are crucial for treating bacterial infections.
- Emerging antibiotic resistance necessitates the development of novel antimicrobial agents.
Purpose of the Study:
- To evaluate the in vitro inhibitory and bactericidal activity of cefpirome against Gram-positive cocci.
- To compare the efficacy of cefpirome with other beta-lactam antibiotics.
- To assess the activity of cefpirome against methicillin-resistant Staphylococcus aureus (MRSA) and other resistant strains.
Main Methods:
- Agar dilution method was employed to determine minimum inhibitory concentrations (MICs).
- One hundred strains of Enterococcus faecalis, 40 strains of Staphylococcus aureus, and 60 strains of coagulase-negative staphylococci were tested.
- Bactericidal activity was assessed by determining the reduction in initial inoculum at various cefpirome concentrations.
Main Results:
- Cefpirome exhibited a minimum inhibitory concentration (MIC) range of 2-128 µg/ml against E. faecalis, with MIC50 of 8 µg/ml and MIC90 of 64 µg/ml.
- Mec gene-negative staphylococci showed cefpirome MICs of 0.25-2 µg/ml (MIC50 0.5 µg/ml, MIC90 1 µg/ml).
- Mec gene-positive staphylococci had higher cefpirome MICs (0.5-128 µg/ml, MIC50 2 µg/ml, MIC90 32 µg/ml).
- Optimal bactericidal activity against susceptible strains was observed at 2-4 times the MIC, achieving >99.7% reduction in inoculum.
Conclusions:
- Cefpirome demonstrates significant in vitro inhibitory and bactericidal activity against a range of Gram-positive cocci.
- The antibiotic maintained susceptibility in resistant strains, suggesting potential clinical utility.
- Cefpirome may offer advantages over other cephalosporins in treating Gram-positive bacterial infections.