PubMed · 14576613
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E Clyti, P Couppie, D Sainte-Marie, R Pradinaud. [Post-traumatic ulcerations].. https://pubmed.ncbi.nlm.nih.gov/14576613/
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Aeromonas hydrophila is a ubiquitous Gram-negative bacterium which can cause motile aeromonad septicemia in both fish and humans. A. hydrophila secretes many extracellular proteins associated with pathogenicity and environmental adaptability. In this study, an extracellular proteome map of A. hydrophila AH-1 was constructed. The major extracellular virulence factors were characterized by comparing the proteomes of various deletion mutants with that of the wild type. The results suggested that serine protease was involved in the processing of a toxin and secreted enzymes such as hemolysin, glycerophospholipid-cholesterol acyltransferase and metalloprotease. We also showed that expressions of polar and lateral flagellins were under the control of temperature, FlhA, LafK, and RpoN. In addition, three novel proteins (potential effector proteins including one ExoT-like protein) were revealed to be secreted via the type III secretion system (TTSS) of A. hydrophila AH-1. Another novel finding was the demonstration of a crosstalk between the lateral flagellar system and the TTSS in A. hydrophila. These results showed that proteomics is a powerful tool for characterizing virulence factors. The construction of proteome maps will provide a valuable means of finding potential candidates for developing suitable diagnostics and therapeutics for this emerging pathogen.
A series of transmission studies was conducted to investigate the aetiology, or aetiologies, of emerging fatal epidemic disease syndromes affecting the common frog (Rana temporaria) in Britain. The syndromes, characterized by skin ulceration or systemic haemorrhages, were induced upon exposure to lesion homogenates or cultured ranavirus. The re-isolation of ranavirus from experimentally affected frogs fulfilled Koch's postulates. Aeromonas hydrophila, previously associated with similar lesions, was not significant to disease development. Unexpectedly, disease outcomes were influenced by both the source of agent and the route of exposure, indicating that different ranaviruses with different tissue tropisms and pathogeneses (possibly similar to quasi-species in RNA virus populations) are circulating in the British common frog population. Our findings confirm that ranavirus disease has emerged as an important cause of amphibian mortality in Britain.
Goldfish (Carassius auratus) were exposed to a mixture of herbicides, namely atrazine, simazine, diuron, and isoproturon (ASDI) at a cumulative concentration of 50microg/l for 12 weeks. Control fish and exposed fish were sampled at 4, 8 and 12 weeks of exposure to observe the combined impact of herbicides on non-specific and specific mechanisms of immunity and antioxidant defenses. The antioxidant defenses were evaluated in haemopoietic organs and liver. ASDI-induced stress was reflected as a significant induction of superoxide (O(2)(-)) production in phagocytic cells of head kidney and spleen. In addition, plasma lysozyme activity was consistently high in the treatment group. Specific immunity was assessed by antibody titre responses following immunization of the fish with sheep red blood cells (SRBCs). Antibody titre was reduced throughout the period of observation in ASDI-treated fish. This reduction was found to be significant at week 4 (p<0.05). Herbicide-exposed fish showed reduced resistance against pathogen invasion but remarkable enhancement in lysozyme activity. The ASDI-induced oxidative stress in spleen, kidney and liver was reflected as a change in the antioxidant enzyme activities in these vital organs of fish. Our data indicate that herbicides at concentrations present in water bodies in Europe cause immune suppression in goldfish.