The increased resistance of pathogenic bacteria to traditional therapy has forced the implementation of different therapies. The consequent use of more than one antibacterial drug can increase toxicity problems, an undesirable situation, especially when it comes to therapy for immunosuppressed patients. Bacterial resistance to different drugs is a war between "humans and bacteria". For this reason, it is important to keep looking for new alternatives for the treatment of pathogenic bacteria. In this study, we determined the antimicrobial activity of methanolic extracts of Lippia graveolens, Sphagneticola trilobata and Gliricidia sepium against four pathogenic bacteria: Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus.  Pseudomonas aeruginosa was the strain most affected by antagonistic activity of all the extracts evaluated, followed by E. coli and S. aureus. We found that S. trilobata was the plant with the highest activity. We carried out tests mixing extracts (1:1) from different parts of each plant, where there was antagonistic and synergistic activity. These results are very promising, since these bacteria are currently being studied for their high resistance mechanisms to a wide variety of antibiotics.