DETAILED DESCRIPTION The invention combines three fluorogenic compounds to facilitate the detection of growth of the majority of clinically significant Gram positive organisms, staphylococci, streptococci, enterococci, and listeriae from between about 31/2-15 hours.
The combination of the three compounds is added to the growth control and to every concentration of the antimicrobial agents compartments.
Growth of the organism is detected by an increase in fluorescence units.
As the organism grows, enzymes are produced which hydrolyze the fluorogenic compound(s), thus releasing the fluorophore, which, when excited by light in the 340-370 nm range, fluoresces in the 440-470 nm range.
If the organism does not grow, the fluorophore part is not released from the compound, and there is no increase in fluorescence at the selected wavelength.
After the organism has grown for between 31/2-15 hour, the amount of fluorescence in the individual concentrations of the antimicrobial agents can be compared to the amount of fluorescence in the growth control, and the minimal inhibitory concentrations of each antimicrobial agent can be determined.
The advantage of utilizing a combination of fluorogenic compounds to detect growth, is the rapidity with which growth and consequently minimal inhibitory concentrations can be determined.
Conventional minimal inhibitory concentration determinations, which rely on turbidity, require 15-24 hours of incubation prior to reading.
Using a combination of certain compounds allows one to determine minimum inhibitory concentrations for the majority of Gram positive organisms, however, within 31/2-15 hours.
Several combinations of fluorogenic compounds were tested and this combination detected growth of most species of Gram positive organisms.
The compounds are leucine-7-amido-4-methylcoumarin, phenylalanine-7-amido-4-methylcoumarin, and 4-methylumbelliferyl phosphate.
This combination detected the majority of clinically relevant species of staphylococci, streptococci, enterococci, and listeriae
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