JoVE Encyclopedia of Experiments
Microbiology
0 views • 5:35 min • August 29th, 2025
Isolate Gram-positive bacterial colonies from a culture plate and suspend them in a medium.
Dilute the suspension to achieve the optimal bacterial concentration for the assay.
Inoculate the test wells of a microplate containing increasing concentrations of a lipoglycopeptide antibiotic and a growth control well containing only the medium.
Spread an aliquot from the control well onto culture plates to verify culture purity and for bacterial count.
Incubate to allow bacterial growth, during which the cell wall is synthesized.
The antibiotic binds to peptidoglycan, a cell wall component, and its precursors, inhibiting polymerization and weakening the wall.
The disruption allows osmotic pressure to cause cell lysis.
After incubation, confirm culture purity and optimal bacterial count.
Inspect the wells for bacterial growth.
The control well shows visible growth, while the the test well with the lowest antibiotic concentration that completely inhibits growth indicates the minimum inhibitory concentration (MIC).
In this demonstration, one freshly prepared plate will be inoculated. To prepare the inoculum, select several well isolated colonies from an 18 to 24 hour blood agar or other non-selective
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