ABSTRACT. The antibacterial activity of ethanol, methanol, hexane and acetone-based extracts of the macroalgae Padina gymnospora (PG), Hypnea musciformes (HM), Ulva fasciata (UF) and Caulerpa prolifera (CP) was investigated. The disk diffusion method was used to evaluate the algae antimicrobial effect against standard strains of Vibrio parahaemolyticus, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella enterica and five virulent antibiotic-resistant strains of V. brasiliensis, V. xuii and V. navarrensis (isolated from the hemolymph of Litopenaeus vannamei). Ethanol extracts of PG and HM inhibited all Vibrio strains. E. coli and P. aeruginosa were only susceptible to ethanol extracts of PG. Among the methanol extracts, only UF was bioactive, inhibiting V. navarrensis. The observed inhibitory effect of ethanol extracts of PG, HM and UF against virulent antibiotic-resistant bacteria suggests these macroalgal species constitute a potential source of bioactive compounds.

ABSTRACT. The phenotypic characterization of 100 Vibrio strains isolated from the hemolymph of cultured Pacific white shrimp, Litopenaeus vannamei, was performed. This process allowed the identification of 10 species: V. navarrensis (n = 53), V. brasiliensis (n = 15), V. parahaemolyticus (n = 10), V. xuii (n = 8), V. cholerae (n = 5), V. coralliilyticus (n = 4), V. neptunis (n = 2), V. alginolyticus (n = 1), V. diazotrophicus (n = 1), and V. vulnificus B3 (n = 1). These results suggest that penaeid hemolymph may be colonized by vibrios with no imposition or necessity of pathological compromising.Key words: Vibrio, phenotypic characterization, hemolymph. RESUMEN. Se realizó la caracterización fenotípica de 100 cepas de Vibrio aisladas de la hemolinfa de camarones Litopenaeus vannameicultivados. Este proceso permitió la identificación de 10 especies: V. navarrensis (n = 53), V. brasiliensis (n = 15), V. parahaemolyticus (n = 10), V. xuii (n = 8), V. cholerae (n = 5), V. coralliilyticus (n = 4), V. neptunis (n = 2), V. alginolyticus (n = 1), V. diazotrophicus (n = 1) y V. vulnificus B3 (n = 1). Los resultados sugieren que la hemolinfa de los peneidos puede ser colonizada por vibrios sin comprometer la salud animal.Palabras clave: Vibrio, caracterización fenotípica, hemolinfa.