药物信息为ERY-TAB (KAISER FOUNDATION HOSPITALS): Microbiology

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  • Erythromycin acts by inhibition of protein synthesis by binding 50 S ribosomal subunits of susceptible organisms. It does not affect nucleic acid synthesis. Antagonism has been demonstrated in vitro between erythromycin and clindamycin, lincomycin, and chloramphenicol.

    Many strains of Haemophilus influenzae are resistant to erythromycin alone, but are susceptible to erythromycin and sulfonamides used concomitantly.

    Staphylococci resistant to erythromycin may emerge during a course of erythromycin therapy.

    Erythromycin has been shown to be active against most strains of the following microorganisms, both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section.

    Gram-positive Organisms

    Corynebacterium diphtheriae

    Corynebacterium minutissimum

    Listeria monocytogenes

    Staphylococcus aureus (resistant organisms may emerge during treatment)

    Streptococcus pneumoniae

    Streptococcus pyogenes

    Gram-negative Organisms

    Bordetella pertussis

    Legionella pneumophila

    Neisseria gonorrhoeae

    Other Microorganisms

    Chlamydia trachomatis

    Entamoeba histolytica

    Mycoplasma pneumoniae

    Treponema pallidum

    Ureaplasma urealyticum

    The following in vitro data are available, but their clinical significance is unknown.

    Erythromycin exhibits in vitro minimal inhibitory concentrations (MIC's) of 0.5 mcg/mL or less against most (= 90%) strains of the following microorganisms; however, the safety and effectiveness of erythromycin in treating clinical infections due to these microorganisms have not been established in adequate and well-controlled clinical trials.

    Gram-positive Organisms

    Viridans group streptococci

    Gram-negative Organisms

    Moraxella catarrhalis

    Susceptibility TestsDilution Techniques

    Quantitative methods are used to determine antimicrobial minimum inhibitory concentrations (MIC's). These MIC's provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MIC's should be determined using a standardized procedure. Standardized procedures are based on a dilution method1 (broth or agar) or equivalent with standardized inoculum concentrations and standardized concentrations of erythromycin powder. The MIC values should be interpreted according to the following criteria:

    MIC (mcg/mL)Interpretation
    = 0.5Susceptible (S)
    1-4Intermediate (I)
    = 8Resistant (R)

    A report of "Susceptible" indicates that the pathogen is likely to be inhibited if the antimicrobial compound in the blood reaches the concentrations 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 which 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 concentrations usually achievable; other therapy should be selected.

    Standardized susceptibility test procedures require the use of laboratory control microorganisms to control the technical aspects of the laboratory procedures. Standard erythromycin powder should provide the following MIC values:

    MicroorganismMIC (mcg/mL)
    S. aureus ATCC 292130.12-0.5
    E. faecalis ATCC 292121-4
    Diffusion Techniques

    Quantitative methods that require measurement of zone diameters also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. One such standardized procedure2 requires the use of standardized inoculum concentrations. This procedure uses paper disks impregnated with 15-mcg erythromycin to test the susceptibility of microorganisms to erythromycin.

    Reports from the laboratory providing results of the standard single-disk susceptibility test with a 15-mcg erythromycin disk should be interpreted according to the following criteria:

    Zone Diameter (mm)Interpretation
    = 23Susceptible (S)
    14-22Intermediate (I)
    = 13Resistant (R)

    Interpretation should be as stated above for results using dilution techniques. Interpretation involves correlation of the diameter obtained in the disk test with the MIC for erythromycin.

    As with standardized dilution techniques, diffusion methods require the use of laboratory control microorganisms that are used to control the technical aspects of the laboratory procedures. For the diffusion technique, the 15-mcg erythromycin disk should provide the following zone diameters in these laboratory test quality control strains:

    MicroorganismZone Diameter (mm)
    S. aureus ATCC 2592322-30
  • Drug Information Provided by National Library of Medicine (NLM).
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