The aim of this study was to evaluate antimicrobial potential of methanolic plant extracts: Carya illinoensis (Wangenh.) K. Koch, Selaginella lepidophylla (Hook. and Grev.) Spring, Euphorbia antisyphilitica Zucc., and Jatropha dioica Sesse. Plant samples were collected from northern Mexico and the extracts were tested against reference bacteria (RS): Staphylococcus aureus (BAA44) and Klebsiella pneumoniae (9180) and clinical isolated bacteria (CB): Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa and Escherichia coli. Antimicrobial activity was performed with Steers Replicator, the LD50 was evaluated with Artemia salina bioassay, and a phytochemical screening was done with colorimetric tests. The extracts showed a minimum inhibitory concentration of 500 ug/mL and LD50 of 1000 ug/mL. The phytochemical tests were positive for flavonoids, lactones, quinones, triterpenes and sterols. C. illinoensis, S. lepidophilla and J. dioica had high correlations (2 0.969) to inhibit the growth of S. aureus (RS and CB), K. pneumoniae (RS) and K. pneumoniae (CB) (p = 0.080, 0.076, 0.016 and 0.029, respectively). The results will contribute to the knowledge of plants used in Mexican traditional medicine.