Hygiene of Eggs

Question 1

1. Where is the most likely place for bacteria to grow in an egg and why?
2. Why are eggs fairly non-perishable?

Answer 1

1. Yolk – glucose-containing.
2. The yolk is at the centre of the egg where there are lots of barriers surrounding it.

Question 2

Factors causing egg spoilage.

Answer 2

Moulds
Pseudomonas
Bacillus

Question 3

1. What layer provides protection the the egg?
2. If eggs washed, what can occur and how can this be rectified?

Answer 3

1. Cuticle – clear layer outside shell.
2. Removal of cuticle can be rectified by replacing with soap, wax, oil or cactus juice.

Question 4

1. How can the shelf life of an egg be increased?
2. Other egg preservation?

Answer 4

1. Refrigerate – Slows denaturing of proteins and slows bacterial growth.
2. Water glass – sodium silicate.
   Lime water
   Wood ashes and tea.

Question 5

1. When was salmonella first recognised in eggs?
2. What salmonella serovar?
3. What is it associated with?

Answer 5

1. 1930s
2. Salmonella enterica Typhimurium.
3. Dirty/wet eggs and shells.

Question 6

Vehicles of infection of salmonella in eggs.

Answer 6

Raw egg
- Tiramisu
- Mousse
- Ice cream
- Egg nog
- Mayonnaise
Under-cooked egg
- Scotch eggs
- Boiled/fried egg
- Meringue
- Egg sandwiches
* mass produced products.

Question 7

International perspective of Salmonella spp as human pathogens.

Answer 7

~ 1.3 billion cases worldwide per year.
~ 3 million deaths.
>5 million cases in Europe each year.
Risk of death up 3x greater in year post-infection.
Chance events.
Sustained infection in food animals.
Eggs and poultry meat major vehicles.

Question 8

Consequence of handling turtles.

Answer 8

100,000 children ill
1500 hospitalisations
40 deaths.

Question 9

1. How can the chances of salmonella in housed birds be reduced?
2. How is control different in extensive systems?
3. What will protect in all systems? – constraints.

Answer 9

1. Biosecurity
   Feed hygiene/additions
   Rodent control
2. Options more limited.
3. Vaccination. – shorter life spans of laying hens so not enough time for immune response.

Question 10

Importance of invasive salmonella?

Answer 10

In chickens, most salmonella stay in the gut.
Faecal contamination of carcasses.
Contamination of egg shells.
A few serovars/strains are naturally invasive.
Present a much greater risk to public health.
E.g Salmonella Enteritidis.

Question 11

How does Salmonella Enteritidis occur?

Answer 11

Migrates from gut to the oviduct and colonises ova, meaning the eggs are laid, freshly contaminated in the yolk.
Is subclinical disease.
Causes inflammation at the oviduct and causes more ova to be released, so more eggs produced.

Question 12

Statutory controls in the UK.

Answer 12

Enteritidis and Typhimurium are ‘of public health importance’ and are the only serotypes of Salmonella that are regulated.
Slaughter of layers or broilers no longer necessary.
Eggs from infected flocks cannot go directly for human consumption. They go as category B where they will be cooked or pasteurised (expensive).

Question 13

NCP for Salmonella.

Answer 13

Must take samples if you produce eggs on a commercial basis.
Flock does not need testing if ….
- all production is for private domestic use (not entering market).
- the premises has fewer than 350 hens and supplies the consumer direct (such as through farm-gate sales or local retailers).

Question 14

What is the ‘lion code’?

Answer 14

Code of practice for the production of eggs in UK by large producers.
Lion stamp on egg as well as producer it’s come from to track egg back to where it has come from.
Recommend vac against the two major salmonellas.