Pharmacological strategies are predicated on targeting differences between prokaryotic bacterial and eukaryotic host cells. Selective toxicity can be achieved by (1) attacking targets unique to bacteria, (2) attacking targets in bacteria similar but not identical to those in host cells, and (3) attacking targets that are shared, but vary in importance between bacteria and host cells (Figure 5).32 Drugs targeting unique differences are the least toxic to host cells.
Antibacterial agents are either bactericidal or bacteriostatic. Bactericidal drugs attack targets essential for bacterial survival, e.g., inhibitors of cell wall synthesis and most inhibitors of DNA synthesis and integrity.32 Bacteriostatic drugs attack targets that are necessary for bacterial growth but not for survival, e.g., most inhibitors of transcription and translation.32 Since bacteriostatic drugs block bacterial replication, they antagonize the effects of bactericidal drugs.