Background: The marine macroalgae are very diverse group of benthonic photosynthetic
organisms. These organisms are a source of a high variety of phytocompounds useful to the human
kind, demonstrating several applications in the human and animal nutrition, in the pharmaceutical,
cosmetic, food and biotechnological industries. Several bioactivities were reported, as antioxidant,
anti-inflammatory, immune-modulatory, antiviral and antimicrobial, indicating the huge pharmacological
potential of this group. Gracilaria cervicornis (Turner) J. Agardh, (Gracilariaceae) is a red
macroalgae which is studied less for its pharmacological applications, mainly against multi-resistant
Objective: The objective of this work was to determine the Minimal Inhibitory Concentration
(MIC) and the antibiotic-modulatory effect of the dichloromethane/methanol extract of G. cervicornis
(DEMGC) against standard and multi-drug resistant clinical isolates (MDRs).
Methods: The MIC of the antibiotics (aminoglycosides) were determined alone or in association
with ECG by the microdilution method. The assays were performed in triplicate and the results
were statistically analyzed using the geometric mean.
Results: The ECG did not demonstrate a clinically relevant antibacterial effect (MIC ≥1024
µg/mL), however, when in association with gentamicin, ECG potentiated significantly the antibiotic
effect against the MDR strains of Pseudomonas aeruginosa 10 and Escherichia coli 06 (p<0.001),
indicating a synergism.
Conclusion: These results indicated that products from G. cervicornis can be used to combat the
bacterial drug multi-resistance, being a source of new drugs or formulations of antibiotics.