In Vitro Antibacterial Testing

A key step in drug discovery is screening assays to assess antibacterial activity of compounds.  We offer a set of assays in key bacterial families.  We can help you select appropriate assays for your compound and mechanism of action.  We can also develop custom assays tailored to your specific program.  If you don't see what you need or have any other questions, please contact us.

Minimum Inhibitory Concentration (MIC) – MIC is the lowest concentration of a particular antibiotic needed to inhibit visible growth of bacteria. This assay is typically performed on planktonic (free floating) bacterial cells. MIC is determined by broth microdilution followed by inoculation onto agar plates for enumeration. We can also test MIC of antibiotics using disk diffusion assays.

Minimum bactericidal concentration (MBC) - MBC is the lowest concentration of antibiotic required to kill an organism. To determine the MBC, cultures are incubated with serial dilutions of the compound(s) of interest, inoculated onto agar plates and enumerated. A colony count that represents 0.1% (99.9% reduction) of the original inoculum is considered as MBC.

Minimum doubling time/growth curve (MDT) – MDT is the time required for the bacterial population to double.  The MDT assay shows the effect of antibiotics on bacterial growth.  To determine MDT, bacterial isolates are grown with and without compound in broth culture.  Optical density values are recorded at multiple timepoints. MDT is calculated by comparing the optical densities at the timepoints.


Bacterial species Number of isolates available Details
Methicillin-Sensitive Staphylococcus aureus 21 Clinical and standard laboratory strains including 1 isogenic pair
Methicillin-Resistant Staphylococcus aureus 14 Clinical and standard laboratory strains including 2 isogenic pairs
Pseudomonas aeruginosa 12 Clinical strains
Acinetobacter baumannii 20 Clinical strains
Enterobacter aerogenes 1 Clinical strains
Enterobacter cloacae 6 Clinical strains including ESBL, MDR, AMPC
Streptococcus pneumoniae 4 Clinical strains
Moraxella catarrhalis 3 Clinical strains
Bacillus subtilis 1  
Escherichia Coli 1