Examinando por Autor "Romero, Alex"
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Ítem Addressing viral and bacterial threats to salmon farming in Chile: historical contexts and perspectives for management and contro(Wiley-Blackwell, 2019-05) Figueroa, Jaime; Cárcamo, Juan; Yañez, Alejandro; Olavarria, Victor; Ruiz, Pamela; Manríquez, René; Muñoz, Claudio; Avendaño-Herrera, Ruben; Romero, AlexThe rapid growth of the salmon farming industry in Chile has led to the appearance of various viral, bacterial, parasitic, and fungal pathogens affecting farmed fish. The Chilean salmon industry has suffered several health crises associated with high fish mortalities, such as caused by the infectious salmon anaemia virus (2007) and harmful algal blooms (2016). In addition to these events, marine farms are continuously affected by outbreaks of harmful pathogens, including the bacteria Piscirickettsia salmonis and, most recently, a reappearance of Renibacterium salmoninarum, and the infectious pancreatic necrosis virus. These outbreaks have led to stricter regulations, but the salmon farming industry continues to struggle despite reforms. In addition to the aforementioned pathogens, which are a continuous threat, other apparently under control pathogens have also reappeared in recent years. In this review, we analyse the current state of knowledge on four of the main pathogens affecting salmon farming in Chile. The infectious pancreatic necrosis virus is relevant as it affects freshwater-stage fish, with survivors then acting as carriers. The infectious salmon anaemia virus currently appears to be under control; however, P. salmonis and R. salmoninarum continue to be the cause for high mortalities in the Chilean aquaculture industry. © 2019 The Authors. Reviews in Aquaculture Published by John Wiley & Sons Australia, LtdÍtem Aloe vera reduces gut inflammation induced by soybean meal in Atlantic salmon (Salmo salar)(Frontiers Media S.A., 2022) Fehrmann-Cartes, Karen; Vega, Matías; Vera, Frank; Enríquez, Ricardo; Feijóo, Carmen G.; Allende, Miguel L.; Hernández, Adrián J.; Romero, AlexPlant-based protein sources, such as soybean, are widely used in fish nutrition due to their market availability, wide distribution and acceptable nutritional quality. However, in some fish species, soybean meal-based diets cause gut inflammation, decreasing both nutrient absorption and growth rates. A suitable alternative to avoid these problems could be the application of additives with anti-inflammatory activity to the diet. In this study, an Aloe vera (Aloe barbadensis Miller, AV) extract was analyzed as a dietary additive to reduce the gut inflammation in Atlantic salmon (Salmo salar) fed with soybean meal (SBM) diet. Fish were distributed in four duplicated groups and fed 28 days with fish meal control diet (FM), AV inclusion diet (AV), FM diet supplemented with AV (FM+AV), SBM diet to induce enteritis and SBM+AV. The fish gut response to these treatments was analyzed in distal intestine by histopathological scores, tissue morphometric measurements and immune gene expression parameters. The score results in fish fed with SBM-based diet clearly showed enteritis, meanwhile fish fed with AV supplemented diet significantly reduced the intestinal SBM signs of damage. These findings were associated to reduction of goblet cells number, lamina propria thickness and sub-epithelial mucosa size, with a significant decrease on pro-inflammatory cytokine il-1β to basal levels, similar to those present in fish fed FM diets. In conclusion, the administration of AV in salmon diet showed a protective intestinal activity against the detrimental effects of SBM, opening the possibility to improve its use as a feed additive in aquafeeds. Copyright © 2022 Fehrmann-Cartes, Vega, Vera, Enríquez, Feijóo, Allende, Hernández and Romero.Ítem Effect of florfenicol on Piscirickettsia salmonis biofilm formed in materials used in salmonid nets, nylon and high-density polyethylene(John Wiley and Sons Inc, 2023) Oliver, Cristian; Ruiz, Pamela; Vidal, José Miguel; Carrasco, Carlos; Escalona, Carla Estefanía; Barros, Javier; Sepúlveda, Daniela; Urrutia, Homero; Romero, AlexPiscirickettsiosis is the most prevalent bacterial disease affecting seawater salmon in Chilean salmon industry. Antibiotic therapy is the first alternative to counteract infections caused by Piscirickettsia salmonis. The presence of bacterial biofilms on materials commonly used in salmon farming may be critical for understanding the bacterial persistence in the environment. In the present study, the CDC Biofilm Reactor® was used to investigate the effect of sub- and over-MIC of florfenicol on both the pre-formed biofilm and the biofilm formation by P. salmonis under the antibiotic stimuli on Nylon and high-density polyethylene (HDPE) surfaces. This study demonstrated that FLO, at sub- and over-MIC doses, decreases biofilm-embedded live bacteria in the P. salmonis isolates evaluated. However, it was shown that in the P. salmonis Ps007 strain the presence of sub-MIC of FLO reduced its biofilm formation on HDPE surfaces; however, biofilm persists on Nylon surfaces. These results demonstrated that P. salmonis isolates behave differently against FLO and also, depending on the surface materials. Therefore, it remains a challenge to find an effective strategy to control the biofilm formation of P. salmonis, and certainly other marine pathogens that affect the sustainability of the Chilean salmon industry. © 2023 John Wiley & Sons Ltd.Ítem First identification of Francisella noatunensis subsp. orientalis causing mortality in mexican tilapia oreochromis spp(Inter-Research, 2016-08) Ortega, Cesar; Mancera, Gerardo; Enríquez, Ricardo; Vargas, Augusto; Martínez, Simón; Fajardo, Raúl; Avendaño-Herrera, Rubén; Navarrete, María José; Romero, AlexFrancisellosis, an emerging disease in tilapia Oreochromis spp., is caused by the fac ultative, intracellular bacterium Francisella noatunensis subsp. orientalis, which is present in var ious countries where tilapia farming is commercially important. We confirmed the presence of francisellosis in Mexican tilapia cultures in association with an outbreak during the second semes ter of 2012. Broodstock fish presented a mortality rate of approximately 40%, and disease was characterized by histologically classified granulomas, or whitish nodules, in different organs, mainly the spleen and kidney. Through DNA obtained from infected tissue and pure cultures in a cysteine heart medium supplemented with hemoglobin, F. noatunensis subsp. orientalis was ini tially confirmed through the amplification and analysis of the 16S rRNA gene and the internal transcribed spacer region. Phylogenetic analysis of these genes demonstrated close similarity with previously reported F. noatunensis subsp. orientalis sequences obtained from infected tilapia from various countries. The identification of this subspecies as the causative agent of the outbreak was confirmed using the iglC gene as a target sequence, which showed 99.5% identity to 2 F. noatunen sis subsp. orientalis strains (Ethime-1 and Toba04). These findings represent the first documented occurrence of francisellosis in Mexican tilapia cultures, which highlights the importance of estab lishing preventative measures to minimize the spread of this disease within the Mexican aqua - culture industry.Ítem New insight into the biological activity of Salmo salar NK-lysin antimicrobial peptides(Frontiers Media SA, 2024-01) Ortega, Leonardo; Carrera, Crisleri; Muñoz-Flores, Carolina; Salazar, Santiago; Villegas, Milton F.; Starck, María F.; Valenzuela, Ariel; Agurto, Niza; Montesino, Raquel; Astuya, Allisson; Parra, Natalie; Pérez, Ercilia T.; Santibáñez, Natacha; Romero, Alex; Ruíz, Pamela; Lamazares, Emilio; Reyes, Fátima; Sánchez, Oliberto; Toledo, Jorge R.; Acosta, JannelNK-lysin is a potent antimicrobial peptide (AMP) with antimicrobial activity against bacteria, fungi, viruses, and parasites. NK-lysin is a type of granulysin, a member of the saposin-like proteins family first isolated from a pig’s small intestine. In previous work, for the first time, we identified four variants of nk-lysin from Atlantic salmon (Salmo salar) using EST sequences. In the present study, we reported and characterized two additional transcripts of NK-lysin from S. salar. Besides, we evaluated the tissue distribution of three NK-lysins from S. salar and assessed the antimicrobial, hemolytic, and immunomodulatory activities and signaling pathways of three NK-lysin-derived peptides. The synthetic peptides displayed antimicrobial activity against Piscirickettsia salmonis (LF-89) and Flavobacterium psychrophilum. These peptides induced the expression of immune genes related to innate and adaptive immune responses in vitro and in vivo. The immunomodulatory activity of the peptides involves the mitogen-activated protein kinases-mediated signaling pathway, including p38, extracellular signal-regulated kinase 1/2, and/or c-Jun N-terminal kinases. Besides, the peptides modulated the immune response induced by pathogen-associated molecular patterns (PAMPs). Our findings show that NK-lysin could be a highly effective immunostimulant or vaccine adjuvant for use in fish aquaculture.Ítem Resistance-nodulation-division efflux pump acrAB is modulated by florfenicol and contributes to drug resistance in the fish pathogen Piscirickettsia salmonis(Oxford University Press, 2016-06) Sandoval, Rodrigo; Oliver, Cristian; Valdivia, Sharin; Valenzuela, Karla; Haro, Ronie E.; Sánchez, Patricio; Olavarría, Víctor H.; Valenzuela, Paulina; Avendaño-Herrera, Rubén; Romero, Alex; Cárcamo, Juan G.; Figueroa, Jaime E.; Yáñez, Alejandro J.Piscirickettsia salmonis is a fastidious intracellular pathogen responsible for high mortality rates in farmed salmonids, with serious economic consequences for the Chilean aquaculture industry. Oxytetracycline and florfenicol are the most frequently used antibiotics against P. salmonis, but routine use could contribute to drug resistance. This study identified differentiated florfenicol susceptibilities in two P. salmonis strains, LF-89 and AUSTRAL-005. The less susceptible isolate, AUSTRAL-005, also showed a high ethidium bromide efflux rate, indicating a higher activity of general efflux pump genes than LF-89. The P. salmonis genome presented resistance nodulation division (RND) family members, a family containing typical multidrug resistance-related efflux pumps in Gram-negative bacteria. Additionally, efflux pump acrAB genes were overexpressed in AUSTRAL-005 following exposure to the tolerated maximal concentration of florfenicol, in contrast to LF-89. These results indicate that tolerated maximum concentrations of florfenicol can modulate RND gene expression and increase efflux pump activity. We propose that the acrAB efflux pump is essential for P. salmonis survival at critical florfenicol concentrations and for the generation of antibiotic-resistant bacterial strains.