Antibiotic Sensitivity Testing
Antibiotic Sensitivity Testing - Related Videos
13:39
Antibiotic Susceptibility Testing: Epsilometer Tests to Determine MIC Values of Two Antibiotics and Evaluate Antibiotic Synergy
0 Views •
2023
Source: Anna Bläckberg1, Rolf Lood1 1 Department of Clinical Sciences Lund, Division of Infection Medicine, Biomedical Center, Lund University, 221 00 Lund Sweden Knowledge of the interactions between antibiotics and bacteria is important in understanding how microbes evolve antibiotic resistance. In 1928, Alexander Fleming discovered penicillin, an antibiotic that exerts its antibacterial function by interfering with cell wall regeneration (1). Other antibiotics with diverse mechanisms of...
12:30
Testing Visual Sensitivity to the Speed and Direction of Motion in Lizards
0 Views •
Cited by 2 •
2006
Testing visual sensitivity in lizards using an operant conditioning paradigm that employs video playback of random-dot kinematograms and computer-generated invertebrates.
05:35
A Broth Microdilution Method for Antibiotic Susceptibility Testing of Gram-Positive Bacteria
0 Views •
2025
Source: Koeth, L. M., et. al., A Reference Broth Microdilution Method for Dalbavancin In Vitro Susceptibility Testing of Bacteria that Grow Aerobically. J. Vis. Exp. (2015).This video demonstrates the broth microdilution method for determining the minimum inhibitory concentration (MIC) of a lipoglycopeptide antibiotic against Gram-positive bacteria. It covers bacterial colony isolation, dilution, inoculation of microplate wells with varying antibiotic concentrations, and verification of culture...
12:41
Stress-induced Antibiotic Susceptibility Testing on a Chip
0 Views •
Cited by 5 •
2014
We have developed a microfluidic platform for rapid antibiotic susceptibility testing. Fluid is passed at high speeds over bacteria immobilized on the bottom of a microfluidic channel. In the presence of stress and antibiotic, susceptible strains of bacteria die rapidly. However, resistant bacteria can survive these stressful conditions.
09:00
Testing the Role of Multicopy Plasmids in the Evolution of Antibiotic Resistance
0 Views •
Cited by 5 •
2018
Here we present an experimental method to test the role of multicopy plasmids in the evolution of antibiotic resistance.
FAQs
A standardized bacterial inoculum makes results comparable by controlling the amount of microorganism exposed to the drug. If the starting bacterial population varies substantially, the measured inhibition may reflect inoculum differences rather than antibiotic activity. Standardization therefore strengthens interpretation of growth suppression and helps investigators compare susceptibility results across isolates tested in the same framework.
Zone diameter and MIC provide different measurements of the same experimental outcome. A disk-based assay records the size of the growth-free area surrounding a drug-impregnated disk, whereas a concentration-based assay identifies the minimum inhibitory concentration, or MIC. The former summarizes spatial inhibition; the latter expresses the lowest tested drug concentration associated with inhibition.
Breakpoints convert a measured zone diameter or MIC into an interpretive category such as susceptible or resistant. They are essential because a raw number alone does not indicate whether the organism is likely to be inhibited under the testing framework. Applying established thresholds allows results to guide targeted therapy and distinguish clinically relevant resistance patterns.
Different microorganism isolates can show different responses to the same antibiotic because susceptibility is an isolate-specific property measured by the assay. Comparing inhibition zones or MICs across isolates can therefore reveal resistant organisms and broader resistance patterns. This distinction matters when treatment must be targeted rather than selected without isolate-specific evidence.
A typical workflow begins by preparing a standardized bacterial inoculum, then exposing it to an antibiotic using either drug-impregnated disks or defined antibiotic concentrations. After exposure, investigators assess growth inhibition as a zone diameter or MIC. Finally, they compare that measurement with established breakpoints to classify the isolate and support treatment or surveillance decisions.
Disk-based and concentration-based formats differ mainly in how inhibition is reported. A drug-impregnated disk produces a zone diameter, while exposure to antibiotic concentrations produces an MIC. Both measurements can be interpreted against established breakpoints, but they preserve different kinds of quantitative information: one describes the extent of growth-free space, and the other identifies the inhibitory concentration measured in the assay.
In infection research, these results connect microorganism behavior with treatment decisions by identifying isolates that are inhibited or resistant to particular antibiotics. Testing clinical and environmental isolates also generates resistance-pattern data for surveillance, including tracking emerging resistance. In practice, this evidence supports targeted therapy, reduces ineffective drug use, and contributes to antimicrobial stewardship.