MIC ( g/ mL) Interpretation 2 Susceptible (S) 4 Intermediate (I) 8 Resistant (R) A report of "Susceptible" indicates that the pathogen is likely to respond to monotherapy with azithromycin. 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 also provides a buffer zone which prevents small uncontrolled technical factors from causing major discrepancies in interpretation. A report of "Resistant" indicates that usually achievable drug concentrations are unlikely to be inhibitory and that other therapy should be selected. Measurement of MIC or MBC and achieved antimicrobial compound concentrations may be appropriate to guide therapy in some infections. (See CLINICAL PHARMACOLOGY section for further information on drug concentrations achieved in infected body sites and other pharmacokinetic properties of this antimicrobial drug product.) Standardized susceptibility test procedures require the use of laboratory control microorganisms. Standard azithromycin powder should provide the following MIC values: Microorganism MIC ( g/ mL) Escherichia coli ATCC 25922 2.0-8.0 Enterococcus faecalis ATCC 29212 1.0-4.0 Staphylococcus aureus ATCC 29213 0.25-1.0 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 procedure 2 that has been recommended for use with disks to test the susceptibility of microorganisms to azithromycin uses the 15-µ g azithromycin disk. Interpretation involves the correlation of the diameter obtained in the disk test with the minimal inhibitory concentration (MIC) for azithromycin. | ||||
Email this article
Printer friendly
Bookmark this pageadvertisement
