salmonella

Question 1

First recognised as

Answer 1

the agent of typhoid fever by Eberth in 1880

Question 2

characteristics

Answer 2

Gram-negative motile non-sporing rod

Question 3

Sterotypes

Answer 3

2400 different serotypes according to the Kauffman-White scheme

67 ‘O’ antigens, cell wall lipopolysaccharide
H antigens from flagella

Serotypes named according to particular combination of O and H antigens

Question 4

Salmonella enterica 7 subspecies

Answer 4

I, II, IIa, IIIb, IV, V and VI

Question 5

Most food poisoning strains come from which subspecies

Answer 5

1 - Salmonella Typhimurium

Question 6

group 1

Answer 6

adapted to man
Salmonella serovars Typhi, Paratyphi
Cause enteric fever

Question 7

group 2

Answer 7

adapted to animals
serovar Dublin, Typhimurium: Cattle
serovar Cholerae-suis: pigs
serovars Galinarum, Pullorum: poultry
Can cause enteric fever type diseases

Question 8

group 3

Answer 8

non host- adapted
2400 serovars carried asymtomatically in animals and birds
cause food poisoning in humans

Question 9

Incubation time

Answer 9

6- 48hr

Question 10

symptom?
can last for ?
Chronic consequences

Answer 10

Nausea, vomiting, diarrhoea, abdominal cramp, fever, headache
May last for 1 -7 days
Chronic consequences may arise several weeks later e.g. arthritis

Question 11

Fatality

Answer 11

usually less than 1% (compared with up to 10% with Typhi)

During Enteritidis outbreaks, 3.6% mortality in nursing homes among elderly

Question 12

Virulence mechanisms
how many genes involve?
Located in ?

Answer 12

• 30 genes approx. involved in invasion phenotype
• Located in ‘pathogenicity island’ 35-40 kb
• Contact-dependent Type III secretion system delivers bacterial proteins to host cells
• Contact with enterocytes triggers formation of invasomes for attachment
• Bacterial signals cause polymerisation of host cell actin and cytoskeletal rearrangements
• Ruffles and blebs form on host cell surface and draw salmonellae into cells
• Salmonella multiplies in vacuoles
• Penetration of Salmonella into cytoplasm of epithelial cells triggers an influx of leucocytes at the infected area
• Release of prostglandins causes mucosal inflammation
• Bacterial cells release an enterotoxin within inflamed tissue which activates host adenyl cyclase enzyme
• This results in fluid loss from gut and diarrhoea

Question 13

Salmonella Enteritidis

associated food

Answer 13

undercooked egg dishes

poultry meat

Question 14

Salmonella Typhimurium associated food

Answer 14

Beef, dairy produce, pork lamb, chicken turkey

Question 15

Other serotypes associated food

Answer 15

Cheese, salami, cream-filled desserts, shrimp, frog legs, yeast, coconut, sauces and salad dressing, cake mixes, dried gelatin, peanut butter, cocoa, and chocolate

Question 16

Infectious dose

Answer 16

depends on serotype host susceptibility and food matrix

• Salmonella Anatum in eggnog: 10^6 – 10^7
• Salmonella Typhimurium in chocolate ~ 10 cells

Question 17

Once salmonella in which food is hard to detect?

Answer 17

fatty food

Question 18

Possible control measures in the poultry flock in 1980’s

Answer 18

Testing for infection

slaughter of positive flocks

Question 19

Possible control measures in the poultry flock in 1997

Answer 19

Strict biosecurity and hygiene in poultry sheds

Vaccination against S. Enteritidis

Question 20

Possible control measures in the poultry flock in The future

Answer 20

Competitive exclusion

Bacteriophage control

Question 21

Broiler Production

Answer 21

Salmonella-free-parent stock

• -> Clean eggs taken to hatcheries, incubated for 21 d
• -> Chicks vaccinated at one day old
• -> Kept in broiler house for 43 days ~2.2 kg. Disinfection of house between batches
• -> Dispatched for slaughter

Question 22

Zoonoses Order 1989

Answer 22

• Testing for Salmonella
• Compulsory slaughter of Salmonella-infected poultry
• Compensation for infected flocks
• Stricter reporting requirements

Question 23

Egg Production

Answer 23

Breeding flocks

• -> Hatcheries
• -> Rearing farms 0-16 weeks
• -> Laying farms 16-72 weeks
• -> Packing centres

Question 24

Lion Code of Practice

control points

Answer 24

Breeding Flocks
Rearing farms
Laying farms
Feed
Transport of eggs from the farm
Packing centres
Best before dates

Question 25

Lion Code of Practice for Breeding Flocks

Answer 25

Tested weekly for Salmonella. Flocks positive for S. Enteritidis and S. Typhimurium are slaughtered.

Feed has to be heat- or acid-treated.
Parent birds are Salmonella-free: They are not vaccinated against Salmonella

Question 26

Lion Code of Practice for Rearing farms & Laying farms

Answer 26

Hygiene measures especially cleaning and disinfection process between flocks.
Effective rodent control.
All pullets are vaccinated against Salmonella Enteritidis on the rearing farm.

Question 27

Lion Code of Practice for Feed

Answer 27

All Lion feed mills must be approved.
All feed must be produced according to the UFAS Code of Practice.
No mammalian or avian products can be used.
No growth promoters can be used.

Question 28

Lion Code of Practice for Transport of eggs from the farm

Answer 28

Temperature control below 20’C.
The use of standardized Keyes tray colours.
Written proof of identity. This ensures traceability of the eggs.

Question 29

Lion Code of Practice for Packing centres

Answer 29

Written HACCP controls.
Cleaning schedules that have to be signed off when completed.
Full traceability. Able to know which flock produced the eggs.
Effective crack and blood detection on eggs.

Question 30

Lion Code of Practice for Best before dates

Answer 30

Best before dates are stamped on the box and on each eggshell along with the Lion logo.