Salmonella

Question 1

What is diff about salmonell classification

Answer 1

Typically written classifying serovars as these are what we are interested in, not species as only two species exist

Question 2

Detection methods of salmonella

Answer 2

Based on unique metabolism aspects, specific activities like H2S prod
Also serotyping, antibio res, phage analysis, genome struct analysis by pilse field gene electrophoresis

Question 3

Where salmonella found

Answer 3

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)

Question 4

Salmonella enteritis infection

Answer 4

Watery foul smelling sometimes mucus or blood cont diarrhoea

Cause dehydration, electrolyte loss and acid/base imbalance

Question 5

Salmonella septicaemia infection

Answer 5

Fever, appetite loss, depression, red milk yield in cattle, infections are severe and acute sometimes fatal
Major issue for large poultry units

Question 6

Salmonella abortion infection

Answer 6

Rare but low level infection can be act during pregnancy

Question 7

Salmonella broad groupings

Answer 7

Generally host specific

V broad host range

Question 8

Host specificity general effect on infection and the caviat

Answer 8

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

Question 9

Zoonotic risks

Answer 9

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

Question 10

Poultry infection

Answer 10

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

Question 11

What other than vacc does lion code give

Answer 11

Biosecurity improvement measures and best before dates

Question 12

Pig infection

Answer 12

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)

Question 13

Pig salmonella testing

Answer 13

Current meat juice ELISA test under zoonoses action plan

Maybe vacc in future

Question 14

Sheep infection

Answer 14

Diarizonae

Infection during preg can cause abortion

Question 15

Cattle infection

Answer 15

Dublin host spec
Typhim non spec
Can cause enteritis

Question 16

Epidemiology

Answer 16

Sewage 
Contam feed
Wild birds and rodents
Human infection
See diagram

Question 17

Salmonella key difference to e coli

Answer 17

Induce their own uptake into euk cells

Capable of invading epi cells lining GIT esp small intestine

Question 18

Salmonella-euk cell contact and uptake

Answer 18

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

Question 19

Important effector pros driving salmonella uptake

Answer 19

SipA
SopB
SopE
They hijack cell pathways eg by mimick euk pro

Question 20

Action inside the cell

Answer 20

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

Question 21

Important effector pros in 2nd secr system

Answer 21

SpiC
SseL
SifA

Question 22

What lead to diarrhoea

Answer 22

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

Question 23

Pathogenicity island 1

Answer 23

Req for epi cell invasion

Encodes T3SS-1 that jnduces mem ruffling cytoskel rearrangement and bact uptake

Question 24

Pathigenicity island 2

Answer 24

Req for bact survival and multiplic in phagosome

Encodes T3SS-2 and preferentially expressed in host cell

Question 25

Other key virulence factors

Answer 25

Fimbriae
Flagella
Fe acquisition systems
Signal transduction systems (allow appropriate T3SS-2 expr)

Question 26

Main Difference between hist spec and non spec serovars

Answer 26

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’

Question 27

How Thyphi and some dublin dissem by stealth

Answer 27

Partly due to Vi capsule masking LPS

Question 28

Typhoid assoc serovars trafficking and dis causing

Answer 28

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

Question 29

Salmonella vacc use

Answer 29

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