PATHOGENICITY OF VIBRIO ANGUILLARUM IN FISH

This dissertation. reports the first detailed study of the possible pathogenic mechanisms and virulence determinants of the fish pathogen V. anguillarum carried out in association with histo-pathological studies using electron microscopy and electrocardiography In addition, possible infection route (s) were investigated and the effect of environmental variables on pathogenesis examined. Pathogenicity was found to be species specific with strains which were avirulent in eels being highly virulent in grey mullet. Following injection of virulent bacteria into eels all tissues were rapidly colonised, death being characterised by severe haemorrhagic septicaemia. In contrast, avirulent strains were rapidly eliminated from the eel host to levels below detection. The heart was particularly affected during pathogenesis. Vibriosis was found to be temperature related, disease being retarded by low temperature. Pathogenic properties investigated included production of enzymes and haemolysins and examined in vitro phagocytosis and growth rates. Membrane proteins were extracted by various techniques and separated using SDS-polyacrylamide electrophoresis thereby elucidating interstrain variation in protein profile, most strains containing a major outer membrane protein thought to be a porin. Ultrastructural studies revealed some bacteria to have up to three polar flagella per cell, with multiflagellate forms only being observed in virulent strains. Analysis of plasmid DNA revealed a partial correlation between possession of a 47 megadalton plasmid and colistin resistance. Experimental vibriosis was characterised by deposition of haemosiderin in liver tissues, thought to be a poorly studied host defence mechanism, and large numbers of tissue bacteria surrounded by an electron lucent zone which was non-capsular in nature. Features of the disease included desquamation of the intestinal mucosa with excessive loss of ions into the gut lumen. The most likly route of infection was thought to be via the gut, as osmoregulatory processes provided a direct means for waterborne V. anguillarum to enter the gut, to which this bacterium was found to be particularly well adapted. Gut traversal was thought to be the precursor to a possible latent infection in the kidney

Methods In:Practical Laboratory Bacteriology

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Serodiagnosis of Salmonella enterica serovar Typhi and S. enterica serovars Paratyphi A, B and C human infections

The aim of this study was to evaluate an immunoassay for the detection of human serum antibodies to the LPS and flagellar antigens of Salmonella Typhi and Salmonella Paratyphi A, B and C, and to the Vi capsular polysaccharide of S. Typhi and S. Paratyphi C. A total of 330 sera were used; these originated from 15 patients who were culture-positive for S. Typhi and 15 healthy controls, together with 300 sera submitted to the Laboratory of Enteric Pathogens for Salmonella serodiagnosis. By SDS-PAGE/immunoblotting, all 15 sera from culture-positive patients had serum antibodies to the 9,12 LPS antigens and 10 had antibodies to the ‘d’ flagellar antigens. Of the 300 reference sera, 22 had antibodies to the 9,12 LPS antigens, one to the 1,4,5,12 LPS antigens and 12 to the 6,7 LPS antigens. Only two sera had antibodies to flagellar antigens, one of which bound to the ‘b’ and the other to the ‘d’ antigen. An ELISA was developed that successfully detected serum antibodies to the Vi capsular polysaccharides, but because of the kinetics of serum antibody production to the Vi, these antibodies may be of limited value in the serodiagnosis of acute infection with S. Typhi and S. Paratyphi C. The immunoassays described here provide a sensitive means of detecting serum antibodies to the LPS, flagellar and Vi antigens of S. Typhi and S. Paratyphi, and constitute a viable replacement for the Widal assay for the screening of sera. The Salmonella serodiagnosis protocols described here are the new standard operating procedures used by the Health Protection Agency's National Salmonella Reference Centre based in the Laboratory of Enteric Pathogens, Colindale, UK

The Relationship between aerobic fitness and recovery from high intensity intermittent exercise

Hemolytic uremic syndrome (HUS), the leading cause of acute renal failure in childhood, can be caused by different serotypes of vero cytotoxin (VT; i.e., Shiga toxin)-producing Escherichia coli (VTEC). Recently, VT was shown to bind to polymorphonuclear leukocytes (PMNL) in the systemic circulation of patients with HUS. This study investigated whether VT bound to PMNL could be detected in persons in households with patients with HUS. Serum antibodies against E. coli O157 and, when available, fecal samples from patients with HUS and household members were studied for the presence of VTEC infection. The circulating PMNL of 82% of the household members were positive for VT, whereas stool and/or serum examination showed only 21% positivity. Thus, current methods underestimate the number of infected persons in households with patients with HUS