The present invention provides methods for identifying target genes whose partial or complete functional inactivation potentiates the activity of an antibiotic agent, e.g., a quinolone antibiotic. The invention further provides methods for identifying agents that modulate expression of target genes or that modulate activity of expression products of target genes. Agents identified according to various methods of the invention potentiate the activity of antibiotics such as quinolones, aminoglycosides, peptide antibiotics and β-lactams. Also provided are agents that suppress and/or retard resistance to antibiotics. The inventive methods provide potentiating agents and compositions comprising potentiating agents and antibiotics. Such agents and compositions can be used for inhibiting growth or survival of a microbial cell or of treating a subject suffering from or susceptible to a microbial infection.