Natural Antimicrobial Peptides: Pleiotropic Molecules in Host Defense

Natural antimicrobial peptides (AMPs) are small cationic molecules that display antimicrobial activity against a wide range of bacteria, fungi and viruses. AMPs are multifunctional molecules that have an essential activity in infection and inflammation: they play an important role in the innate immune response, not only as antimicrobial agents, but also as immunomodulating molecules and as an important link between the innate and adaptive immune response. In this article, we will discuss the antimicrobial activity, together with the novel properties of some of these molecules as immune modulators on the innate and adaptive immune response.Fil: Sanchez, Mercedes Leonor. Universidad de Buenos Aires. Facultad de Medicina. Cátedra de Farmacología; ArgentinaFil: Martínez, Melina María Belén. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Microbiología Molecular; ArgentinaFil: Maffia, Paulo Cesar. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Microbiología Molecular; Argentin

Antimicrobial activity of de novo designed cationic peptides against multi-resistant clinical isolates

Antibiotic resistance is one of the main problems concerning public health or clinical practice. Antimicrobial peptides appear as good candidates for the development of new therapeutic drugs. In this study we de novo designed a group of cationic antimicrobial peptides, analyzed its physicochemical properties, including its structure by circular dichroism and studied its antimicrobial properties against a panel of clinical isolates expressing different mechanisms of resistance. Three cationic alpha helical peptides exhibited antimicrobial activity comparable to, or even better than the comparator omiganan (MBI-226).Fil: Faccone, Diego Francisco. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas. Área de Antimicrobianos; ArgentinaFil: Veliz, Omar. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas. Área de Antimicrobianos; ArgentinaFil: Corso, Alejandra. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas. Área de Antimicrobianos; ArgentinaFil: Noguera, Martín Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Martínez, Melina María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Microbiología Molecular; ArgentinaFil: Payés, Cristian. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Microbiología Molecular; ArgentinaFil: Semorile, Liliana Carmen. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Microbiología Molecular; ArgentinaFil: Maffia, Paulo Cesar. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Microbiología Molecular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Antimicrobial peptides: Interaction with model and biological membranes and synergism with chemical antibiotics

Antimicrobial peptides (AMPs) are promising novel antibiotics since they have shown antimicrobial activity against a wide range of bacterial species, including multiresistant bacteria; however, toxicity is the major barrier to convert antimicrobial peptides into active drugs. A profound and proper understanding of the complex interactions between these peptides and biological membranes using biophysical tools and model membranes seems to be a key factor in the race to develop a suitable antimicrobial peptide therapy for clinical use. In the search for such therapy, different combined approaches with conventional antibiotics have been evaluated in recent years and demonstrated to improve the therapeutic potential of AMPs. Some of these approaches have revealed promising additive or synergistic activity between AMPs and chemical antibiotics. This review will give an insight into the possibilities that physicochemical tools can give in the AMPs research and also address the state of the art on the current promising combined therapies between AMPs and conventional antibiotics, which appear to be a plausible future opportunity for AMPs treatment.Fil: Hollmann, Axel. Universidad Nacional de Santiago del Estero; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes; ArgentinaFil: Martínez, Melina María Belén. Universidad Nacional de Quilmes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Maturana, Patricia del Valle. Universidad Nacional de Santiago del Estero; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Semorile, Liliana Carmen. Universidad Nacional de Quilmes; ArgentinaFil: Maffia, Paulo Cesar. Universidad Nacional de Quilmes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Transglutaminase binding fusion protein linked to SLPI reduced corneal inflammation and neovascularization

Background: To study the effect of topical administration of a fusion protein (PF-MC) made up of N-terminal portion of the protease inhibitor Trappin-2 (which is a substrate of transglutaminasa-2) and SLPI (protein with anti-inflammatory, anti-bacterial and anti-viral ability), in an animal model of corneal inflammation and angiogenesis. Methods: An alkali injury was produced with a filter paper of 3 mm with 1 N NaOH during 40 seconds on the right cornea of 36 male Sprague Dawley rats, under general anesthesia. Animals were divided into three groups according to treatment. Group 1 was treated with 10 ul of PF-MC (200 ug/ml; n = 12), Group 2, with 10 ul of SLPI (200 ug/ml; n = 12) and Group 3 was treated with buffer (10 ul; n = 12) topically administered four times a day for up to 7 days. Half of the animals were sacrificed at day 3 before making a re-epithelialization time analysis with fluorescein staining at 18 and 24 hours. In the remaining animals corneal opacity was studied and digital photographs were taken at day 7 before doing euthanasia. Eyes were processed for histology and immunofluorescence. Results: Corneal ulcerated area was significantly lower in PF-MC treated animals compared to SLPI and buffer-treated animals at 18 hours and 24 hours postinjury. A clear cornea and fundus red reflex was only found among PF-MC treated animals. Histological analysis revealed a stratified corneal epithelium with at least three layers in all PF-MC animals at day 7. In this group there was a reduced number of PMNs in the corneal stroma at 3 and 7 days of follow-up. Besides, corneal neovascularization was much more extended in SLPI and Buffer animals than in animals treated with PF-MC. Conclusions: The binding of SLPI with Cementoin to transglutaminase seems to be an effective strategy to treat corneal inflammation and angiogenesis.Fil: Salica, Juan Pablo. Universidad Austral. Facultad de Ciencias Biomedicas; Argentina. Hospital Universitario Austral. Departamento de Oftalmología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Guerrieri, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Centro de Estudios Farmacológicos y Botánicos; Argentina. Universidad de Buenos Aires. Facultad de Medicina; ArgentinaFil: Maffia, Paulo Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Centro de Estudios Farmacológicos y Botánicos; Argentina. Universidad de Buenos Aires. Facultad de Medicina; ArgentinaFil: Croxatto, Juan Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación Oftalmología Argentina "J. Malbrán"; ArgentinaFil: Chuluyan, Hector Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Centro de Estudios Farmacológicos y Botánicos; Argentina. Universidad de Buenos Aires. Facultad de Medicina; ArgentinaFil: Gallo, Juan Eduardo Maria. Universidad Austral. Facultad de Ciencias Biomedicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Hospital Universitario Austral. Departamento de Oftalmología; Argentin

Farmacogenética en psiquiatría: ¿qué tan lejos estamos de su aplicación clínica?

La farmacogenética estudia cómo la variabilidad genética influye en la respuesta de los pacientes a los fármacos. Esta disciplina tendría mayor impacto en la práctica de aquellas especialidades médicas que tratan enfermedades complejas en las que la respuesta terapéutica es insuficiente y/o tiene elevados costos como es el caso de la psiquiatría. La presente es una revisión narrativa en la que se analizan los principales resultados de los estudios de farmacogenética realizados con los grupos de psicofármacos más relevantes y se analiza que falta para la incorporación de estos avances a nuestra práctica cotidiana. Se concluye que, a pesar de los notables progresos en el campo de la farmacogenética en los últimos 10 años, los estudios en psiquiatría no han sido concluyentes y que la utilización clínica de las pruebas de farmacogenética es aún muy limitada. No obstante, hay ciertos elementos alentadores acerca de la posibilidad de aplicación de estas herramientas para optimizar los tratamientos psiquiátricos.Pharmacogenetics studies how genetic variation influences the response of patients to drugs. This discipline has a greater impact in those medical specialties that treat complex diseases in which the therapeutic response is insufficient and/or have high costs such as psychiatry. This is a narrative review in which we analyze the main results of pharmacogenetic studies performed with the most relevant groups of psychoactive drugs and discusses missing for incorporating these advances into our daily practice. We conclude that despite the remarkable progress in the field of Pharmacogenetics in the last 10 years, studies in psychiatry have been inconclusive and the clinical use of pharmacogenetic testing is still limited. However, there are some encouraging elements about the applicability of these tools for the improvement of psychiatric treatments.Fil: Daray, Federico Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Cátedra de Farmacología; ArgentinaFil: Maffia, Paulo Cesar. Universidad Nacional de Quilmes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rothlin, Rodolfo Pedro. Universidad de Buenos Aires. Facultad de Medicina. Cátedra de Farmacología; ArgentinaFil: Errasti, Andrea Emilse. Universidad de Buenos Aires. Facultad de Medicina. Cátedra de Farmacología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Cationic antimicrobial peptides inactivate shiga toxin-encoding bacteriophages

Shiga toxin (Stx) is the principal virulence factor during Shiga toxin-producing Escherichia coli (STEC) infections. We have previously reported the inactivation of bacteriophage encoding Stx after treatment with chitosan, a linear polysaccharide polymer with cationic properties. Cationic antimicrobial peptides (cAMPs) are short linear aminoacidic sequences, with a positive net charge, which display bactericidal or bacteriostatic activity against a wide range of bacterial species. They are promising novel antibiotics since they have shown bactericidal effects against multiresistant bacteria. To evaluate whether cationic properties are responsible for bacteriophage inactivation, we tested seven cationic peptides with proven antimicrobial activity as anti-bacteriophage agents, and one random sequence cationic peptide with no antimicrobial activity as a control. We observed bacteriophage inactivation after incubation with five cAMPs, but no inactivating activity was observed with the random sequence cationic peptide or with the non-alpha helical cAMP Omiganan. Finally, to confirm peptide-bacteriophage interaction, zeta potential was analyzed by following changes on bacteriophage surface charges after peptide incubation. According to our results we could propose that: (1) direct interaction of peptides with phage is a necessary step for bacteriophage inactivation, (2) cationic properties are necessary but not sufficient for bacteriophage inactivation, and (3) inactivation by cationic peptides could be sequence (or structure) specific. Overall our data suggest that these peptides could be considered a new family of molecules potentially useful to decrease bacteriophage replication and Stx expression.Fil: del Cogliano, Manuel Eugenio. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Ingeniería Genética y Biología Molecular y Celular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Hollmann, Axel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Santiago del Estero. Universidad Nacional de Santiago del Estero. Centro de Investigaciones y Transferencia de Santiago del Estero; Argentina. Universidad Nacional de Quilmes; ArgentinaFil: Martínez, Melina María Belén. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnologia. Instituto de Microbiologia Basica y Aplicada. Laboratorio de Micologia Molecular.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Semorile, Liliana Carmen. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnologia. Instituto de Microbiologia Basica y Aplicada. Laboratorio de Micologia Molecular.; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Ingeniería Genética y Biología Molecular y Celular; ArgentinaFil: Ghiringhelli, Pablo Daniel. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Ingeniería Genética y Biología Molecular y Celular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Maffia, Paulo Cesar. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnologia. Instituto de Microbiologia Basica y Aplicada. Laboratorio de Micologia Molecular.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bentancor, Leticia Verónica. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Ingeniería Genética y Biología Molecular y Celular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Synergistic and antibiofilm activity of the antimicrobial peptide P5 against carbapenem-resistant Pseudomonas aeruginosa

In the search for new antimicrobial molecules, antimicrobial peptides (AMPs) offer a viable alternative to conventional antibiotics, as they physically disrupt the bacterial membranes, leading to membrane disruption and eventually cell death. In particular, the group of linear α-helical cationic peptides has attracted increasing research and clinical interest. The AMP P5 has been previously designed as a cationic linear α-helical sequence, being its antimicrobial and hemolytic properties also evaluated. In this work, we analyzed the feasibility of using P5 against a carbapenem-resistant clinical isolate of Pseudomonas aeruginosa, one of the most common and risky pathogens in clinical practice. After antimicrobial activity confirmation in in vitro studies, synergistic activity of P5 with meropenem was evaluated, showing that P5 displayed significant synergistic activity in a time kill curve assay. The ability of P5 to permeabilize the outer membrane of P. aeruginosa can explain the obtained results. Finally, the antibiofilm activity was investigated by viability analysis (MTT assay), crystal violet and confocal imaging, with P5 displaying mild biofilm inhibition in the range of concentrations tested. Regarding biofilm disruption activity, P5 showed a higher efficacy, interfering with biofilm structure and promoting bacterial cell death. Atomic force microscope images further demonstrated the peptide potential in P. aeruginosa biofilm eradication, confirming the promising application of P5 in multi-resistant infections therapeutics.Fil: Martínez, Melina María Belén. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Microbiología Molecular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gonçalves, Sónia. Universidade Nova de Lisboa; PortugalFil: Felício, Mário R.. Universidade Nova de Lisboa; PortugalFil: Maturana, Patricia del Valle. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Noa Sur. Centro de Investigación en Biofísica Aplicada y Alimentos. - Universidad Nacional de Santiago del Estero. Centro de Investigación en Biofísica Aplicada y Alimentos; ArgentinaFil: Santos, Nuno C.. Universidade Nova de Lisboa; PortugalFil: Semorile, Liliana Carmen. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Microbiología Molecular; ArgentinaFil: Hollmann, Axel. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Microbiología Molecular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Noa Sur. Centro de Investigación en Biofísica Aplicada y Alimentos. - Universidad Nacional de Santiago del Estero. Centro de Investigación en Biofísica Aplicada y Alimentos; ArgentinaFil: Maffia, Paulo Cesar. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Microbiología Molecular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Green-synthesized silver nanoparticles using Aloe maculata extract as antibacterial agent for potential topical application

Nowadays, antibiotic resistance poses a threat to public health worldwide. For this reason, non-traditional antibacterial products, such as silver nanoparticles (AgNPs), offer an opportunity to address this issue. Although AgNPs have been proven to be effective antimicrobial agents, we studied the antibacterial and antibiofilm effects of two novel AgNPs (AgNP-Aloe-1 and AgNP-Aloe-2) obtained by green synthesis, their cytotoxicity on a cell line derived from human keratinocytes, and their skin penetration. These AgNPs were obtained here for the first time from an Aloe maculata aqueous extract as a reducing and capping agent of Ag(I), with varying the initial silver concentrations (5 and 9 mM of AgNO3 for AgNP-Aloe-1 and AgNP-Aloe-2, respectively). For all the assessments, these were compared with AgNPs obtained from a traditional chemical method employing hydroxylamine hydrochloride as a reducing agent and AgNO3 (AgNP–NH2OH·HCl). The AgNPs were characterized physicochemically by TEM, DLS, Zeta potential, UV–vis, fluorescence, and Raman spectroscopy. Additionally, the concentration of silver forming AgNPs and the reaction yield were determined. Both green-synthesized AgNPs showed an improvement in the inhibition of bacterial growth after 24 h of incubation for E. coli and S. aureus. AgNP-Aloe-1 presented a MIC 4 times lower for both bacteria compared to AgNP–NH2OH·HCl, while AgNP-Aloe-2 presented a MIC 32 and 8 time lower for E. coli and S. aureus, respectively. Moreover, they produced a decrease in the biofilm biomass formation from P. aeruginosa at lower concentrations (6.25 μg/ml for AgNP-Aloe-1 and 1.56 μg/ml for AgNP-Aloe-2) than AgNP-NH2OH·HCl which only showed a reduction of 30% at the maximum concentration tested. However, AgNP-Aloe-1 and AgNP-Aloe-2 were less efficient in eradicating pre-formed biofilm. Even though AgNP-Aloe-2 showed a lower reaction yield (31.7%) compared to AgNP-Aloe-1 (68.5%), they showed the best antibacterial activity. On the other hand, green-synthesized AgNPs were mainly retained in the stratum corneum of intact skin and reached lower concentrations in the viable epidermis than AgNP–NH2OH·HCl. Moreover, AgNP-Aloe-1 and AgNP-Aloe-2 did not show cytotoxic effects on human keratinocytes at the antibacterial concentrations. Their improved performance and lower skin penetration could be attributed to their physicochemical properties, such as size (10–25 nm), charge (around −10 mV), and shape (tendency towards a spherical shape), but mainly to the presence of phytocompounds from the extract that remained attached to the AgNPs, as observed by Raman spectroscopy and UV–vis. For the reasons mentioned above, these novel AgNPs obtained by a more environmentally friendly method have the potential to be used as antibacterial agents, particularly for topical applications.Fil: Franceschinis, Gaston Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Beverina, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; ArgentinaFil: Corleto, Ingrid Merlina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Hurlingham; ArgentinaFil: Sosa, Ayelen Morena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Lillo, Rolando Cristian Rodrigo. Universidad Nacional de Hurlingham; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Arias Cassará, María Lucrecia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; ArgentinaFil: Alonso, Silvia del Valle. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Maffia, Paulo Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Hurlingham; ArgentinaFil: Martinetti Montanari, Jorge Anibal. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Hurlingham; ArgentinaFil: Tuttolomondo, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Calienni, Maria Natalia. Universidad Nacional de Hurlingham; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; Argentin

Antibacterial, anti-biofilm and in vivo activities of the antimicrobial peptides P5 and P6.2

Cationic antimicrobial peptides (AMPs) are short linear amino acid sequences, which display antimicrobial activity against a wide range of bacterial species. They are promising novel antimicrobials since they have shown bactericidal effects against multiresistant bacteria. Their amphiphilic structure with hydrophobic and cationic regions drives their interaction with anionic bacterial cytoplasmic membranes, which leads to their disruption. In this work two synthetic designed AMPs, P5 and P6.2, which have been previously analyzed in their ability to interact with bacterial or eukaryotic membranes, were evaluated in their anti-biofilm and in vivo antibacterial activity. In a first step, a time-kill kinetic assay against P. aeruginosa and S. aureus and a curve for hemolytic activity were performed in order to determine the killing rate and the possible undesirable toxic effect, respectively, for both peptides. The biofilm inhibitory activity was quantified at sub MIC concentrations of the peptides and the results showed that P5 displayed antibiofilm activity on both strains while P6.2 only on S. aureus. Scanning electron microscopy (SEM) of bacteria treated with peptides at their MIC revealed protruding blisters on Gam-negative P. aeruginosa strain, but almost no visible surface alteration on Gram-positive S. aureus. These micrographs highlighted different manifestations of the membrane-disrupting activity that these kinds of peptides possess. Finally, both peptides were analyzed in vivo, in the lungs of neutropenic mice previously instilled with P. aeruginosa. Mice lungs were surgically extracted and bacteria and pro-inflammatory cytokines (IL-β, IL-6 and TNF-α) were quantified by colony forming units and ELISA, respectively. Results showed that instillation of the peptides produced a significant decrease in the number of living bacteria in the lungs, concomitant with a decrease in pro-inflammatory cytokines. Overall, the results presented here suggest that these two new peptides could be good candidates for future drug development for anti-biofilm and anti-infective therapy.Fil: Martínez, Melina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Microbiología Molecular; ArgentinaFil: Polizzotto, Axel Leonel. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Microbiología Molecular; ArgentinaFil: Flores, Naiquen Elizabeth. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Microbiología Molecular; ArgentinaFil: Semorile, Liliana Carmen. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Microbiología Molecular; ArgentinaFil: Maffia, Paulo Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Microbiología Molecular; Argentin