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*''Salmonella'' may be carried sub-clinically
*''Salmonella'' may be carried sub-clinically
*Some human strains cause enteric fever (''S. Typhi'' causes typhoid), also gastroenteritis, septicaemia or bacteraemia
*Some human strains cause enteric fever (''S. Typhi'' causes typhoid), also gastroenteritis, septicaemia or bacteraemia
===Characteristics===
===Characteristics===
*Gram negative bacilli
*Gram negative bacilli
*Facultative intracellular pathogens
*Facultative intracellular pathogens
*Non-lactose fermentor, oxidase negative
*Non-lactose fermentors, oxidase negative
*Do not produce urease or indole from tryptophan
*Do not produce urease or indole from tryptophan
*Utilise citrate as a carbon source
*Utilise citrate as a carbon source
*Reduce nitrates to nitrites
*Reduce nitrates to nitrites
*Grow on MacConkey
*Grow on MacConkey
*Red colonies on brilliant green agar indicating alkalinity
*Ferment glucose to produce acid and gas
*Ferment glucose to produce acid and gas
*Usually produce hydrogen sulphide
*Usually produce hydrogen sulphide - red colinies with black centre on XLD agar
*Most motile with flagellae (H antigen)
*Most motile with flagellae (H antigen)
*H antigen can be in phase 1 or phase 2, depending on a genetic switch allowing for one of the H antigen genes to be transcribed at any one time
*H antigen can be in phase 1 or phase 2, depending on a genetic switch allowing for one of the H antigen genes to be transcribed at any one time
*Categorised into serovars depending on and H (Flagellar) antigen, e.g. ''Salmonella enterica'' subspecies ''enterica'' serovar Tymphimurium; must also determine phase of H antigen (isolates must be in phase 1 to be typed)
*Categorised into serovars depending on and H (Flagellar) antigen, e.g. ''Salmonella enterica'' subspecies ''enterica'' serovar Tymphimurium; must also determine phase of H antigen (isolates must be in phase 1 to be typed)
*Most animal and human isolates in Groups B to E
*Most animal and human isolates in Groups B to E
===Pathogenicity===
===Pathogenicity===
===Diagnosis===
===Diagnosis===
*History of previous outbreaks; clinical signs
*Post mortem: enterocolitis; blood-stained intestinal contents; enlarged mesenteric lymph nodes
*Laboratory confirmation by detection in faeces and blood from live animals; intestinal contents and tissue samples from dead animals
*Isolation from blood or tissues confirms septicaemic salmonellosis
*Heavy growth on plates innoculated with faeces or intestinal contents from infected animals suggests ''Salmonella'' as cause
*Light growth may suggest carrier state
*Culture specimens on BG and XLD agar; also add to enrichment broth such as selinite or tetrathionate broth; incubate plates and broth under aerobic conditions at 37 degrees centigrade for 48 hours; subculture from enrichment broth at 24 and 48 hours
*Suspicious colonies should be identified biochemically by reactions in TSI agar and lysine decarboxylase
*Slide agglutination using antisera for O and H antigens confirm the serotype
*The antigens in both phases of the H antigen must be identified
*Phage typing is used for epidemiological studies of isolates
*A rising antibody titre using paired serum samples in ELISA indicates active infection
===Treatment===
===Treatment===
*Intravenous antibiotics used to treat septicaemic salmonellosis
*Effective antimicrobials include tetracyclines, chloramphenicol, trimethoprim-sulphonamides, ampicillin, amoxicillin, 3rd generation cephalosporins, fluoroquinolones, but depend on the susceptiblity of individual isolate
*Fluid and electrolyte replacent to prevent dehydration and shock
===Control===
===Control===
*Reduce exposure of young animals from fomites, food, water, infected animals
*Avoid stresses e.g. overcrowding
*Purchase animals from reliable sources and isolate incoming animals
*Separate animals according to age
*Rodent control, good hygiene, pasture rotation
*Avoid grazing animals on pasture fertilised by slurry for at least 2 months after spreading
*Attenuated live ''S.'' Typhimurium and ''S.'' Dublin vaccines used in cattle
*Avoid oral prophylactic antimicrobials