Cefditoren microbiology
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Microbiology
Cefditoren is a cephalosporin with antibacterial activity against gram-positive and gram-negative pathogens. The bactericidal activity of cefditoren results from the inhibition of cell wall synthesis via affinity for penicillin-binding proteins (PBPs).
Cefditoren is stable in the presence of a variety of ß-lactamases, including penicillinases and some cephalosporinases. Cefditoren has been shown to be active against most strains of the following bacteria, both in vitro and in clinical infections, as described in the INDICATIONS AND USAGE section.
Aerobic Gram-Positive Microorganisms
- Staphylococcus aureus (methicillin-susceptible strains, including ß-lactamase-producing strains)
- Note: Cefditoren is inactive against methicillin-resistant Staphylococcus aureus
- Streptococcus pneumoniae (penicillin-susceptible strains only)
Aerobic Gram-Negative Microorganisms
- Haemophilus influenzae (including ß-lactamase-producing strains)
- Haemophilus parainfluenzae (including ß-lactamase-producing strains)
- Moraxella catarrhalis (including ß-lactamase-producing strains)
The following in vitro data are available, but their clinical significance is unknown. Cefditoren exhibits in vitro minimum inhibitory concentrations (MICs) of ≤0.125 µg/mL against most (≥90%) strains of the following bacteria; however, the safety and effectiveness of cefditoren in treating clinical infections due to these bacteria have not been established in adequate and well-controlled clinical trials.
Aerobic Gram-Positive Microorganisms
- Streptococcus Groups C and G
- Streptococcus, viridans group (penicillin-susceptible and -intermediate strains)
Susceptibility Tests
Dilution Techniques
Quantitative methods that are used to determine MICs provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. The MICs should be determined using a standardized procedure. Standardized procedures are based on dilution methods1 (broth) or equivalent with standardized inoculum concentrations and standardized concentrations of cefditoren powder. The MIC values obtained should be interpreted according to the following criteria: For testing Haemophilus spp.a and Streptococcus spp. including S. pneumoniaeb:
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a This interpretive standard is applicable only to broth microdilution susceptibility tests with Haemophilus spp. using Haemophilus Test Medium (HTM).
b These interpretive standards are applicable only to broth microdilution susceptibility tests with Streptococcus spp. using cation-adjusted Mueller-Hinton broth with 2-5% lysed horse blood.
Susceptibility test criteria cannot be established for S. aureus
A report of “Susceptible” indicates that the pathogen is likely to be inhibited if the antimicrobial compound in the blood reaches the concentration usually achievable. A report of “Intermediate” indicates that the result should be considered equivocal, and, if the microorganism is not fully susceptible to alternative, clinically feasible drugs, the test should be repeated. This category implies possible clinical applicability in body sites where the drug is physiologically concentrated or in situations where high dosage of drug can be used. This category also provides a buffer zone that prevents small, uncontrolled technical factors from causing major discrepancies in interpretation. A report of “Resistant” indicates that the pathogen is not likely to be inhibited if the antimicrobial compound in the blood reaches the concentration usually achievable and that other therapy should be selected.
Standardized susceptibility test procedures require the use of laboratory control bacterial strains to control the technical aspects of the laboratory procedures. Standard cefditoren powder should provide the following MICs with these quality control strains:
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a This quality control range is applicable to only S. pneumoniae ATCC 49619 tested by a microdilution procedure using cation-adjusted Mueller-Hinton broth with 2-5% lysed horse blood.
b This quality control range is applicable to only H. influenzae ATCC 49247 and ATCC 49766 tested by a microdilution procedure using HTM.[1]
References
Adapted from the FDA Package Insert.