RESUMO
Brazil is one of the world's leading producers of Nile tilapia, Oreochromis niloticus. However, the industry faces a major challenge in terms of infectious diseases, as at least five new pathogens have been formally described in the last five years. Aeromonas species are Gram-negative anaerobic bacteria that are often described as fish pathogens causing Motile Aeromonas Septicemia (MAS). In late December 2022, an epidemic outbreak was reported in farmed Nile tilapia in the state of São Paulo, Brazil, characterized by clinical signs and gross pathology suggestive of MAS. The objective of this study was to isolate, identify, and characterize in vitro and in vivo the causative agent of this epidemic outbreak. The bacterial isolates were identified as Aeromonas veronii based on the homology of 16S rRNA (99.9%), gyrB (98.9%), and the rpoB gene (99.1%). A. veronii showed susceptibility only to florfenicol, while it was resistant to the other three antimicrobials tested, oxytetracycline, enrofloxacin, and amoxicillin. The lowest florfenicol concentration capable of inhibiting bacterial growth was ≤0.5 µg/mL. The phenotypic resistance of the A. veronii isolate observed for quinolones and tetracycline was genetically confirmed by the presence of the qnrS2 (colE plasmid) and tetA antibiotic-resistant genes, respectively. A. veronii isolate was highly pathogenic in juvenile Nile tilapia tested in vivo, showing a mortality rate ranging from 3 to 100% in the lowest (1.2 × 104) and highest (1.2 × 108) bacterial dose groups, respectively. To our knowledge, this study would constitute the first report of highly pathogenic and multidrug-resistant A. veronii associated with outbreaks and high mortality rates in tilapia farmed in commercial net cages in Brazil.
RESUMO
ABSTRACT: The inclusion of sesame oil associated with soybean, linseed and freshwater fish residue oil in the diets fed to Lambaris Astyanax altiparanaewas evaluated by the growth performance parameters, body composition and possible physiological changes (GARUTTI & BRISTSKI, 2000). The experiment was a completely randomized design in two factorial parameters tested: three oil types (soy oil (SO), linseed oil (LO) and freshwater fish residue oil (FRO)), combined or not with sesame oil (SEO), totalizing six treatments and four replications 24 cages, capacity of 0.70m3 (density of 251 fish m-3). The fish (mean weight 2.35g±0.62g and mean length 5.25cm±0.68cm) were fed with the experimental diets twice a day. After 75 days, the following parameters were determined: body chemical composition and fatty acid profile, glycemia, liver (LG) and muscle glycogen (MG) levels, and lipid peroxidation (TBARS). Fish fed with diets containing SEO had higher desaturation index values of LNA while those fed with SEO combined with LO displayed reduced hepatic lipid oxidation. Inclusion of SEO improved the fatty acid profile and stability, without causing problems related to fish performance and health.
RESUMO: Este trabalho fez a inclusão de óleo de gergelim associado ao óleo de soja, de linhaça e de resíduo de peixes de água doce nas dietas para avaliar o desempenho zootécnico, a composição química corporal e as possíveis alterações fisiológicas de lambari Astyanax altiparanae. O delineamento experimental foi inteiramente casualizado, avaliando-se dois parâmetros: três tipos de óleo (óleo de soja (SO), óleo de linhaça (LO) e óleo de resíduo de peixe de água doce (FRO)), associado ou não ao óleo de gergelim (SEO), totalizando seis tratamentos e quatro repetições (24 tanques-rede de capacidade útil de 0,70m3 (densidade de 251 peixes m-3). Os peixes (peso médio 2,35g±0,62g) e comprimento médio de 5,25cm±0,68cm) foram alimentados duas vezes ao dia com as dietas experimentais. Após 75 dias, foram feitas as análises de composição química e perfil de ácidos graxos corporal, glicemia, glicogênio hepático (LG) e muscular (MG), e peroxidação lipídica (TBARS) do tecido hepático. Os indivíduos que receberam dietas contendo SEO apresentaram valores mais altos de taxa de dessaturação de ácido linolênico; aqueles que receberam SEO e LO combinados demonstraram níveis reduzidos de oxidação lipídica do tecido hepático. A inclusão de SEO melhora o perfil de ácidos graxos e a estabilidade, sem provocar problemas relacionados ao desempenho e saúde dos peixes.