Salmonella Flashcards
What is diff about salmonell classification
Typically written classifying serovars as these are what we are interested in, not species as only two species exist
Detection methods of salmonella
Based on unique metabolism aspects, specific activities like H2S prod
Also serotyping, antibio res, phage analysis, genome struct analysis by pilse field gene electrophoresis
Where salmonella found
Intestines of many animals, fish reptiles birds mammals
In most mammals its not commensal, but can be shed asymptomatically by carriers (more likely with birds and reptiles)
Salmonella enteritis infection
Watery foul smelling sometimes mucus or blood cont diarrhoea
Cause dehydration, electrolyte loss and acid/base imbalance
Salmonella septicaemia infection
Fever, appetite loss, depression, red milk yield in cattle, infections are severe and acute sometimes fatal
Major issue for large poultry units
Salmonella abortion infection
Rare but low level infection can be act during pregnancy
Salmonella broad groupings
Generally host specific
V broad host range
Host specificity general effect on infection and the caviat
Host spec often cause more serious systemic dis, broad host range often restricted to the gut and may cause gastroenteritis (often zoonotic too)
These only apply to healthy outbred adults, infected orally
Zoonotic risks
Main risks typhimurium and enteritidis mainly from pigs and poultry
Non host spec strains that cause gastro enteritis
2/3 of cases in UK
Virchow and hadar also emerging non spec strains
Poultry infection
Most asymptomatic
Host spec: pullorum and gallinarum
Mostly elim by serology testing and slaughter
Non spec: typhim and enteritidis
Layer and broiler vacc under lion codes cause red
Vertical transmission possible as ovary infection causes yolk sac infection and diseased chick
What other than vacc does lion code give
Biosecurity improvement measures and best before dates
Pig infection
Typhimurium most commonly isolated from pigs
Acute infection cause vomit pyrexia diarrhoea can be followed by carrier state
Choleraesuis cause swine fever/hog cholera (species spec)
Pig salmonella testing
Current meat juice ELISA test under zoonoses action plan
Maybe vacc in future
Sheep infection
Diarizonae
Infection during preg can cause abortion
Cattle infection
Dublin host spec
Typhim non spec
Can cause enteritis
Epidemiology
Sewage Contam feed Wild birds and rodents Human infection See diagram
Salmonella key difference to e coli
Induce their own uptake into euk cells
Capable of invading epi cells lining GIT esp small intestine
Salmonella-euk cell contact and uptake
Initial contact via flagella and fimbriae
Salmonella expr at least 2 T3 secr syst, one injects effector pros causing cytoskel changes causing bact invasion
Enter inside a salmonella cont vacuole
Target microfold/M cells for invasion but also invade via enterocytes
Important effector pros driving salmonella uptake
SipA
SopB
SopE
They hijack cell pathways eg by mimick euk pro
Action inside the cell
2nd T3secr syst secr pros into cytoplasm that prev phagosome oxidase assembly and alter trafficking of phagosome to prevent lysosome fusion so red chance of bact being killed in phagosome
Repl until cell death when they are released into lam prop
Important effector pros in 2nd secr system
SpiC
SseL
SifA
What lead to diarrhoea
Cytoskel changes
Signalling pathway interference
Tight jctn disruption
Epi loss
All cause barrier integrity loss and so loss of adaorptic fx
Also IC and bact products recognised by PRRs cause inflam resp lead to fluid and cell influx contrib to diarrhoea
Pathogenicity island 1
Req for epi cell invasion
Encodes T3SS-1 that jnduces mem ruffling cytoskel rearrangement and bact uptake
Pathigenicity island 2
Req for bact survival and multiplic in phagosome
Encodes T3SS-2 and preferentially expressed in host cell
Other key virulence factors
Fimbriae
Flagella
Fe acquisition systems
Signal transduction systems (allow appropriate T3SS-2 expr)
Main Difference between hist spec and non spec serovars
How successfully cleared after initial invasion through epi layer of GIT
If elicit strong intestinal inflam resp often controlled at muc surf via neutro recruitment
Systemic dis assoc dont tend to cause enteritis and may dissem by ‘stealth’
How Thyphi and some dublin dissem by stealth
Partly due to Vi capsule masking LPS
Typhoid assoc serovars trafficking and dis causing
Traffick in blood and lymph to multiple organs (esp liver and spleen) and high bact load here and in blood can cause high inflam resp can cause toxic shock esp LPS
Salmonella vacc use
Elicit good humoral and cell med resp
So att strains used
Can also engineer to express other antig from plasmids to hive protection against things other than salmonella
