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A report of "Susceptible" indicates that the pathogen is likely to be inhibited if the antimicrobial compound in the urine 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 urine reaches the
concentrations usually achievable; other therapy should be selected. Text Continues Below
Standardized susceptibility test procedures require the use of laboratory control microorganisms to control the technical aspects of the laboratory procedures. Standard nitrofurantoin powder should provide the following MIC values: Microorganism MIC (µg/ mL)
E. coli ATCC 25922 4-16
S. aureus ATCC 29213 8-32
E. faecalis ATCC 29212 4-16 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 requires the use of standardized inoculum concentrations. This procedure uses paper disks impregnated with 300 µg nitrofurantoin to test the susceptibility of microorganisms to nitrofurantoin. Macrobid (nitrofurantoin monohydrate/ macrocrystals)
Procter & Gamble Pharmaceuticals 4
Revised March 2003 Reports from the laboratory providing results of the standard single-disk susceptibility test with a 300-µg nitrofurantoin disk should be interpreted according to the following criteria: Page: << Prev | 1 | 2 | 3 | 4 | Next >>
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