importance of serial dilution in research articles

Importance of serial dilution in research articles series#

Only reporting MIC value is not recommended as the physician may fail to interpret it appropriately. Laboratories have to report the interpretive category (susceptible, susceptible-dose-dependent, intermediate or resistant) to the physician with or without MIC value. BD Phoenix system (Becton Dickenson Diagnostics) Reporting MIC results.Some of the automated system approved by the FDA and currently in use are Various commercial automated systems are available for antimicrobial susceptibility testing. Find more about E-test Automated system for The intersection of the lower part of the ellipse-shaped growth inhibition area with the test strip indicates the MIC value. After 18-24 hours incubation, a drop-shaped inhibition zone intersects the graded test strip at the inhibitory concentration of the antibiotic. E-test methodĪ plastic strip with a predefined gradient of one antibiotic is applied onto an inoculated agar plate. Results are observed after incubation at 35☌ for 18-24 hours. Multiple test organisms (at a concentration of 10^4 CFU/mL) can be applied directly or using an inoculum replicating apparatus (steer replicator) on a single agar plate of particular antibiotic concentration. Varying concentrations of antimicrobial agents are added to an agar medium, mostly Mueller Hinton Agar (for non-fastidious organisms). Find more about broth dilution method Agar dilution method Therefore, in this example, the MIC is 6.25 μg/mL.

Importance of serial dilution in research articles series#

However, by convention, the MIC is interpreted as the concentration of the antimicrobial agent contained in the first tube in the series that inhibits visible growth. in the image shown above, the breakpoint of growth inhibition lies between 6.25 (no turbidity is seen) and 3.12 μg/mL (turbidity is still appearing) of antimicrobial agent. Broth dilution susceptibility test (MIC 6.25μg/mL)Į.g. At the end of the incubation period (generally 18-24 hours), the tubes are visually examined for turbidity. Serial dilutions of the test agent are made in a liquid microbial growth medium which is inoculated with a standardized number of organisms and incubated for a prescribed time. The broth/tube dilution test is the standard method for determining levels of microbial resistance to an antimicrobial agent.

1 Minimum Bactericidal Concentration (MBC) Broth dilution method.

MIC gives valuable information, which will help to customize the treatment to direct only the causative bacterium.ĬLSI has recently recommended SDD category reporting instead of “intermediate” when reporting cefepime results for Enterobacteriaceae isolates because there are multiple approved dosing options for cefepime.

MIC is determined only in specific clinical scenarios under the instruction of a Microbiologist, e.g. Conversely, the more resistant the microorganism, the higher the MIC and the smaller the zone of inhibition. The more susceptible the microorganism is to the antimicrobial agent, the lower the MIC and the larger the zone of inhibition. The MIC and the zone diameter of inhibition are inversely correlated. Relationship between MIC and Zone of Inhibition

extensive research that correlates MIC with serum achievable levels for each antimicrobial agent,.

The interpretive criteria for these categories are based on Once the MIC is calculated, it can be compared to known values for a given bacterium and antimicrobial agent and is interpreted as susceptible, susceptible-dose dependent (SSD), intermediate and resistant.

At this dilution the antimicrobial agent is bacteriostatic, i.e some bacteria may still be alive. While performing the dilution method, the lowest concentration (highest dilution) of the antimicrobial preventing appearance of turbidity (growth) is considered as MIC. E-test, tube dilution method and agar dilution methods are employed to determine MIC value. The MIC test determines the antimicrobial activity of a test agent against a specific bacteria. Minimum Inhibitory Concentration (MIC) is defined as the lowest concentration (expressed as mg/L or μg/μL) of an antimicrobial agent that inhibits the visible in-vitro growth of microorganisms.