Table 1.

Characteristics of antibacterial assays for detecting new leads.

Goldman and Laughon: Discovery and Validation of New Antitubercular Compounds as Potential Drug Leads and Probes

Assay	Advantages	Disadvantages
Whole cell growth inhibition	Compound likely enters microbial cells: the cell entry problem is less of an issue Can immediately move to: whole cell mode of action analysis, evaluation of microbial spectrum	Usually a longer assay (many hours to days) Nonspecific compounds acting at the cell surface or intracellularly may be detected Compound could be unstable, sequestered or degraded by cells and thus inactive but analog could be a valid lead Mode of action unknown; may need to determine/validate for further development and to avoid optimizing nonspecific action or target drift
Isolated in vitro enzyme or pathway	Usually a rapid assay (minutes as opposed to hours or days) Target known in advance	Nonspecific compounds may be detected Compound may not enter cells, or could be sequestered or degraded If compound is active on whole cells, the mode of action needs to be confirmed
Hybrid whole cell with specific enzyme or pathway targeted readout	Compound likely enters microbial cells: the cell entry problem is less of an issue Can immediately move to: whole cell mode of action analysis; evaluation of microbial spectrum Target known in advance	Usually a longer assay (many hours to days) More difficult to design The mode of action needs to be confirmed to support further development and to avoid optimizing nonspecific action or target drift Unknown interactions can give false positives that are difficult to unravel Compound could be unstable, sequestered or degraded by cells and thus inactive but analog could be a valid lead