Mechanism of Action
Cefuroxime axetil is a bactericidal agent that acts by inhibition of bacterial cell wall synthesis. Cefuroxime axetil has activity in the presence of some β-lactamases, both penicillinases and cephalosporinases, of gram-negative and gram-positive bacteria.
Mechanism of Resistance
Resistance to cefuroxime axetil is primarily through hydrolysis by β-lactamase, alteration of penicillin-binding proteins (PBPs), decreased permeability, and the presence of bacterial efflux pumps.
Susceptibility to cefuroxime axetil will vary with geography and time; local susceptibility data should be consulted, if available. Beta-lactamase
-negative, ampicillin-resistant (BLNAR) isolates of
H. influenzae should be considered resistant to cefuroxime axetil.
Cefuroxime axetil has been shown to be active against most isolates of the following bacteria, both
in vitro and in clinical infections
[see
Indications and Usage (1)]
:
Staphylococcus aureus (methicillin-susceptible isolates only)
Streptococcus pneumoniae
Streptococcus pyogenes
Escherichia coli
a
Klebsiella pneumoniae
a
Haemophilus influenzae
Haemophilus parainfluenzae
Moraxella catarrhalis
Neisseria gonorrhoeae
a Most extended spectrum β-lactamase (ESBL)
-producing and carbapenemase-producing isolates are resistant to cefuroxime axetil.
· Spirochetes
Borrelia burgdorferi
The following
in vitro data are available, but their clinical significance is unknown. At least 90 percent of the following microorganisms exhibit an
in vitro minimum inhibitory concentration (MIC) less than or equal to the susceptible breakpoint for cefuroxime axetil of 1 mcg/mL. However, the efficacy of cefuroxime axetil in treating clinical infections due to these microorganisms has not been established in adequate and well-controlled clinical trials.
Staphylococcus epidermidis (methicillin-susceptible isolates only)
Staphylococcus saprophyticus (methicillin-susceptible isolates only)
Streptococcus agalactiae
Morganella morganii
Proteus inconstans
Proteus mirabilis
Providencia rettgeri
Peptococcus niger
Susceptibility Test Methods
When available, the clinical microbiology laboratory should provide the results of
in vitro susceptibility tests for antimicrobial drug products used in local hospitals and practice areas to the physician as periodic reports that describe the susceptibility profile of nosocomial and community-acquired pathogens. These reports should aid the physician in selecting an antibacterial drug product for treatment.
Dilution Techniques: Quantitative methods are used to determine antimicrobial MICs. These MICs provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. The MICs should be determined using a standardized test method (broth or agar).
1,2 The MIC values should be interpreted according to criteria provided in Table 10.
2,3
Diffusion Techniques: Quantitative methods that require measurement of zone diameters also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. The zone size provides an estimate of the susceptibility of bacteria to antimicrobial compounds. The zone size should be determined using a standardized test method.
4 This procedure uses paper disks impregnated with 30 mcg cefuroxime axetil to test the susceptibility of microorganisms to cefuroxime axetil. The disk diffusion interpretive criteria are provided in Table 10.
3
Table 10. Susceptibility Test Interpretive Criteria for Cefuroxime Axetil
a For
Enterobacteriaceae,
Haemophilus spp
., and
Moraxella catarrhalis, susceptibility interpretive criteria are based on a dose of 500 mg every 12 hours in patients with normal renal function.
b
Haemophilus spp. includes only isolates of
H. influenzae and
H. parainfluenzae.
|
Pathogen
| Minimum Inhibitory Concentrations (mcg/mL)
| Disk Diffusion Zone Diameters (mm)
|
(S) Susceptible
| (I) Intermediate
| (R) Resistant
| (S) Susceptible
| (I) Intermediate
| (R) Resistant
|
Enterobacteriaceae
a
| ≤4
| 8 to 16
| ≥32
| ≥23
| 15 to 22
| ≤14
|
Haemophilus spp.
a,b
| ≤4
| 8
| ≥16
| ≥20
| 17 to 19
| ≤16
|
Moraxella catarrhalis
a
| ≤4
| 8
| ≥16
| -
| -
| -
|
Streptococcus pneumoniae
| ≤1
| 2
| ≥4
| -
| -
| -
|
Susceptibility of staphylococci to cefuroxime may be deduced from testing only penicillin and either cefoxitin or oxacillin.
Susceptibility of
Streptococcus pyogenes may be deduced from testing penicillin.
3
A report of “Susceptible” indicates that the antimicrobial drug is likely to inhibit growth of the pathogen if the antimicrobial drug reaches the concentration usually achievable at the site of infection. 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 a 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 antimicrobial drug is not likely to inhibit growth of the pathogen if the antimicrobial drug reaches the concentrations usually achievable at the infection site; other therapy should be selected.
Quality Control: Standardized susceptibility test procedures require the use of laboratory controls to monitor and ensure the accuracy and precision of supplies and reagents used in the assay, and the techniques of the individual performing the test.
1,2,4 The QC ranges for MIC and disk diffusion testing using the 30 mcg disk are provided in Table 11.
3
Table 11. Acceptable Quality Control (QC) Ranges for Cefuroxime Axetil
QC Strain
| Minimum Inhibitory Concentrations (mcg/mL)
| Disk Diffusion Zone Diameters (mm)
|
Escherichia coli ATCC 25922
| 2 to 8
| 20 to 26
|
Staphylococcus aureus ATCC 25923
| -
| 27 to 35
|
Staphylococcus aureus ATCC 29213
| 0.5 to 2
| -
|
Streptococcus pneumoniae ATCC 49619
| 0.25 to 1
| -
|
Haemophilus influenzae ATCC 49766
| 0.25 to 1
| 28 to 36
|
Neisseria gonorrhoeae ATCC 49226
| 0.25 to 1
| 33 to 41
|
ATCC = American Type Culture Collection.