Morganella morganii

Proteus inconstans

Proteus mirabilis

Providencia rettgeri

NOTE: Pseudomonas spp., Campylobacter spp., Acinetobacter calcoaceticus, Legionella spp., and most strains of Serratia spp. and Proteus vulgaris are resistant to most first- and second-generation cephalosporins. Some strains of Morganella morganii, Enterobacter cloacae, and Citrobacter spp. have been shown by in vitro tests to be resistant to cefuroxime and other cephalosporins.

Anaerobic Microorganisms

Peptococcus niger

NOTE: Most strains of Clostridium difficile and Bacteroides fragilis are resistant to cefuroxime.

Susceptibility Tests

Dilution Techniques

Quantitative methods that are used to determine MICs provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. One such standardized procedure uses a standardized dilution method¹ (broth, agar, or microdilution) or equivalent with cefuroxime powder. The MIC values obtained should be interpreted according to the following criteria:

A report of “Susceptible” indicates that the pathogen, if in the blood, is likely to be inhibited by usually achievable concentrations of the antimicrobial compound in blood. A report of “Intermediate” indicates that inhibitory concentrations of the antibiotic may be achieved if high dosage is used or if the infection is confined to tissues or fluids in which high antibiotic concentrations are attained. 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 usually achievable concentrations of the antimicrobial compound in the blood are unlikely to be inhibitory and that other therapy should be selected.

Standardized susceptibility test procedures require the use of laboratory control microorganisms. Standard cefuroxime powder should give the following MIC values:

Diffusion Techniques

Quantitative methods that require measurement of zone diameters provide estimates of the susceptibility of bacteria to antimicrobial compounds. One such standardized procedure² that has been recommended (for use with disks) to test the susceptibility of microorganisms to cefuroxime uses the 30-mcg cefuroxime disk. Interpretation involves correlation of the diameter obtained in the disk test with the MIC for cefuroxime.

Reports from the laboratory providing results of the standard single-disk susceptibility test with a 30-mcg cefuroxime disk should be interpreted according to the following criteria:

Interpretation should be as stated above for results using dilution techniques.

As with standard dilution techniques, diffusion methods require the use of laboratory control microorganisms. The 30-mcg cefuroxime disk provides the following zone diameters in these laboratory test quality control strains:

Clinical Studies

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