Salmonella Flashcards
salmonella basic info
- gram negative
- facultatively aerobic
- rod-shaped
- non-lactose fermenter
4 ways to classify salmonella
1) grouping by epidemiological point of view
2) disease syndrome or animal from which they were fist isolated
3) place they were first reported
4) antigenic formula
salmonella groups by epidemioligical point of view
- group 1: only infecting humans
- group 2: adapted for particular species of vertebrates
- group 3: no particular host preferences (paratyphoids)
2 species of salmonella
- S. bongori (humans)
- S. enterica
types of antigenic variation
- phase variation
- H-O variation
- S-R variation
- form variation (O, V-W)
H-O variation
- H = flagellar, O = somatic
- loss of H antigen or flagella (usually only one direction) –> flagellated HO to non-flagellated O
S-R variation
- smooth to rough variation
- not abrupt –> gradual loss of O antigen, exposing core polysaccharide
- low in virulence, can be used as vaccine strains
- flagellar antigens unchanged
V-W variation
- affects Vi (virulence) antigen
- Vi is outermost polysaccharide layer
phase variation
- H antigen often exists in one of two different phases
- flagella with antigens either in phase 1 or 2, may switch back and forth
- no phase variation in non-motile strains
salmonella virulence (5)
- antigenic phase variation
- sequestration of nutritional factors
- resistance to serum killing
- antimicrobial resistance
- pathogenicity islands
what is salmonellosis the leading cause of
foodborne illness worldwide
only human types of salmonella
paratyphi A through C, typhi
salmonella typhi
- causes typhoid fever
- acute gastroenteritis after 7-14 day incubation
- fever, diarrhea, vomiting, abdominal tenderness, death
- multiplies in GI tract, disseminates throughout body through bloodstream
- carriers have it in gallbladder, bile ducts
salmonellosis in poultry
- biggest animal reservoir
- mortality in young chicks, adult birds carry dz
- persists in ovaries –> contaminated eggs
- fecal contamination
types of salmonellosis in poultry
- host-specific: gallimarum, pullorum (both non-motile)
- non host-specific: paratyphoid
salmonella pullorum
- white bacillary diarrhea or pullorum disease
- infects young chicks and turkey poults up to 2-3w old
- high mortality
- depression, anorexia, white fecal pastings, white lung nodules, necrotic lesions
salmonella gallinarum
- fowl typhoid
- ovaries –> egg –> chick –> other chicks
- green/yellow diarrhea, dicolored comb and wattles, lesions
- usually affects growing or adult birds
- high mortaliity rates to chronic infection
- eradicated in the US
paratyphoid salmonella in birds
- contaminated feed products, hatcheries, environment
- egg transmission
- public health importance
best sample for chicken salmonella
cecal junction
salmonella in cattle (host specific)
- S dublin, S tymphimurium
- all ages affected
- acute or chronic (adults can be carriers)
salmonella in cattle (non-host adapted)
- S tymphimurium
- chornic carriers does not occur frequently
- calves: fever, diarrhea
- adults: drop in milk production, fever, diarrhea, can cause death
- humans can be infected!
salmonellosis in pigs (host adapted)
- S choleraesuis, S typhisuis
- choleraesuis most common, causes necrotic enteritis
- typhisuis related to choleraesuis but not common
salmonella in pigs (non-host adapted)
can infect humans
salmonella in horses
- typhimurium, enteritidis, newport, heidelberg
- young animals, stress
- fever, colic, diarrhea
salmonella in dogs
- found in the feces of many normal dogs
- intermittent diarrhea in infected adults
- puppies more susceptible
salmonella in cats
- many serotypes isolated
- eating contaminated food, through feces
- kittens more susceptible –> enteritis
- adults can be carriers or have diarrhea
salmonella in sheep
- many serotypes, S typhimurium
- fever, scouring, blood in feces
- pregnant animals may die of septicemia before aborting
salmonella in wild animals
- turtles and iguanas (pets), frogs are source of infection –> reflect environmental contamination
- captive birds too –> S typhimurium
control of salmonellosis
- treatment: antibiotics for acute form
- control: prevent exposure
