RESUMO
The genus Aeromonas comprises more than thirty Gram-negative bacterial species which mostly act as opportunistic microorganisms. These bacteria are distributed naturally in diverse aquatic ecosystems, where they are easily isolated from animals such as fish and crustaceans. A capacity for adaptation also makes Aeromonas able to colonize terrestrial environments and their inhabitants, so these microorganisms can be identified from different sources, such as soils, plants, fruits, vegetables, birds, reptiles, amphibians, among others. Infectious processes usually develop in immunocompromised humans; in fish and other marine animals this process occurs under conditions of stress. Such events are most often associated with incorrect practices in aquaculture. Aeromonas has element diverse ranges, denominated virulence factors, which promote adhesion, colonization and invasion into host cells. These virulence factors, such as membrane components, enzymes and toxins, for example, are differentially expressed among species, making some strains more virulent than others. Due to their diversity, no single virulence factor was considered determinant in the infectious process generated by these microorganisms. Unlike other genera, Aeromonas species are erroneously differentiated by conventional biochemical tests. Therefore, molecular assays are necessary for this purpose. Nevertheless, new means of identification have been considered in order to generate methods that, like molecular tests, can correctly identify these microorganisms. The main objectives of this review are to explain environmental and structural characteristics of the Aeromonas genus and to discuss virulence mechanisms that these bacteria use to infect aquatic organisms and humans, which are important aspects for aquaculture and public health, respectively. In addition, this review aims to clarify new tests for the precise identification of the species of Aeromonas, contributing to the exact and specific diagnosis of infections by these microorganisms and consequently the treatment.
Assuntos
Aeromonas/classificação , Aeromonas/isolamento & purificação , Doenças dos Animais/microbiologia , Microbiologia Ambiental , Infecções por Bactérias Gram-Negativas/veterinária , Doenças das Plantas/microbiologia , Aeromonas/patogenicidade , Animais , Técnicas Bacteriológicas/métodos , Infecções por Bactérias Gram-Negativas/microbiologia , Humanos , Técnicas de Diagnóstico Molecular/métodos , Virulência , Fatores de Virulência/genéticaRESUMO
The aim of this work was to purify and partially characterize a mannose recognition lectin from Nile tilapia (Oreochromis niloticus) serum, named OniL. OniL was isolated through precipitation with ammonium sulfate and affinity chromatography (Concanavalin A-Sepharose 4B). In addition, we evaluated carbohydrate specificity, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) profiles, and in vitro immunomodulatory activity on mice splenocyte experimental cultures through cytotoxic assays and cytokine production. The ammonium sulfate fraction F2 showed the highest specific hemagglutinating activity (331) and was applied to affinity matrix. Adsorbed proteins (OniL) were eluted with methyl-α-D: -mannopyranoside. OniL, a 17-kDa protein by SDS-PAGE constituted by subunits of 11 and 6.6 kDa, showed highest affinity for methyl-α-D: -mannopyranoside and D: -mannose. Immunological assays, in vitro, showed that OniL did not show cytotoxicity against splenocytes, induced higher IFN-γ production and lower IL-10 as well as nitrite release. In conclusion, OniL lectin was successfully purified and showed a preferential Th1 response in mice splenocytes.