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Standardized susceptibility test procedures require the use of laboratory control microorganisms to control the technical aspects of the laboratory procedures. Standard cefprozil powder should provide the following MIC values: Microorganism MIC (µg/ mL)
Enterococcus faecalis ATCC 29212 4Ð 16
Escherichia coli ATCC 25922 1Ð 46
Haemophilus influenzae ATCC 49766 1Ð 46
Staphylococcus aureus ATCC 29213 0.25Ð 1
Streptococcus pneumoniae ATCC 49619 0.25Ð 1 Diffusion Techniques: Text Continues Below
Quantitative methods that require measurement of zone diameters also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. One such standardized procedure 3 requires the use of standardized inocu-lum concentrations. This procedure uses paper disks impregnated with 30 µg cefprozil to test the susceptibility of microorganisms to cefprozil. Reports from the laboratory providing results of the standard single-disk susceptibility test with a 30 µg cefprozil disk should be interpreted according to the following criteria: Zone diameter (mm) Interpretation
18 Susceptible (S) 15Ð 17 Intermediate (I) 14 Resistant (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 cefprozil. As with standardized dilution techniques, diffusion methods require the use of labora-tory control microorganisms that are used to control the technical aspects of the labo-ratory procedures. For the diffusion technique, the 30 µg cefprozil disk should provide the following zone diameters in these laboratory test quality control strains. Microorganism Zone diameter (mm)
Escherichia coli ATCC 25922 21Ð 27
Haemophilus influenzae ATCC 49766 20Ð 27
Staphylococcus aureus ATCC 25923 27Ð 33
Streptococcus pneumoniae ATCC 49619 25Ð 32 Page: << Prev | 1 | 2 | 3 | 4 | 5
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