Methods are disclosed for identifying antibacterial compounds which inhibit propagation of selected spectrum bacteria, which bacteria use specific tRNA to code for Ala, Met, Ser, or Leu that other bacteria do not use. In one embodiment, the selected spectrum bacteria use GCA to code for Ala, whereas other bacteria use a different codon to code for alanine. The methods involve determining whether putative inhibitors promote or inhibit complex formation between the tRNA and a bacterial ribosome, or between the tRNA and an aminoacyl synthetase. Compounds which promote or inhibit complex formation can disrupt protein production, which bacteria need to propagate. The identified antibacterial compounds can selectively inhibit bacterial propagation. By limiting their effects to the selected spectrum bacteria, these compounds can treat or prevent specific bacterial infections without disrupting the normal bacterial flora, the patients' microbiome, or causing antibacterial resistance.