Hygiene and safety of shell eggs

Question 1

Internal structure of eggs

Answer 1

Outside to inside
- shell - has pores for gas exchange
- shell membrane - contains antimicrobial peptide
- thin albumen - “
- thick albumen -“
- Vitelline membrane
- Yolk- where things (such as bacteria) can grow

Question 2

evolution of eggs

Answer 2

have evolved to be a non perishable item - due to chick not emerging for 21 days

Question 3

Spoilage of eggs

Answer 3

From
Moulds - through the shell pores and grows on them
Pseudomonas- would make it glow fluorescent and smell bad
Bacillus - smells bad

Question 4

shell contaminants

Answer 4

will be slow to penetrate the egg
storing eggs in the fridge will slow protein breakdown and they will resist microbial growth better

cuticle around shell will provide protection by selling the pores

if eggs are washed like in America cuticle is replaced by soap, wax, oil or cactus juice

Question 5

Preservation methods

Answer 5

sodium silicate - an alkaline solution that will keep eggs over winter - keeps shell clean and stops bacterial growth
lime water - does a similar thing

Question 6

Salmonella in eggs

Answer 6

mainly Salmonella enteric server Typhimurium - cause typhoid in mice

associated with dirty/ wet egg shells - contaminate the outside of eggs

Question 7

Vehicles of infection

Answer 7

Raw egg
Undercooked egg

contamination is more likely in mass produced food - catering

salmonella has managed to make its way through the yolk where it can multiply there

Question 8

Salmonella spp. as a human pathogen

Answer 8

Primarily associated with poultry and eggs
risk of death is up 3 times greater in the year post- infection
Sustained infection of food animals

Question 9

Evolution of salmonella

Answer 9

E.coli and salmonella had a common ancestor till they diverged
E.coli to mamas
Salmonella to egg laying things
e.g. dinosaurs, raptors, turtles, birds etc.
enterica species infects birds and now there is 2000+ servers
enterica is pathogenic for mammals

Question 10

Turtles and salmonella

Answer 10

Have evolved to internalise salmonella and spread to any cold blooded animals
Handling them = spread

Question 11

Control in production systems

Answer 11

reduced chance of infection
- biosecurity - mixing outdoors and indoors = biosecurity ruined
- feed hygiene/ additions
- Rodent control - salmonella was originally used in pesticides so mice carry lots of salmonella/ typhoid in mice

options are more limited in extensive systems

VACCINATE

Question 12

Vaccinations

Answer 12

laying hens - can vaccinate against enteritidis* and tychomurium - both servers of salmonella

broilers - used for meat and only like for 5 weeks so not enough time to mount an immune response

Question 13

Caged hens and salmonella

Answer 13

• not going outside - less exposed to rodents - cortisol at low levels as not trying to promote adaptive behaviour

moving to enriched - will start competing for supplies so cortisol levels will increases body is trying to adapt- will mean immune system is less good so will shed more salmonella

Question 14

Invasive salmonella

Answer 14

Most salmonellas usually stays in the gut
here contamination by
- fecal contamination of carcasses in scald tanks
- contamination of eggs
Salmonella enteritidis* is naturally invasive - won’t stay in the gut

Question 15

Egg shells becoming salmonella positive

Answer 15

Egg shells can become salmonella positive at lay
not how SE enters the egg contents

Question 16

Salmonella Enteritidis infections in chickens

Answer 16

instead of staying in gut will migrate to the oviduct an colinises in the ova
SE will cause inflammation in oviduct - will cause release of more ovum so more eggs - survival strategy - economically good?

In most hens SE is subclinical

Question 17

Statutory controls in the UK

Answer 17

Enteritidis and Typhimurium are the only serotypes of salmonella that are regulated - as adapted to eggs and related to lots of lines

slaughter of the infected is no longer necessary
- egg must not go directly for human consumption
- will be a class B egg - for things that will be cooked or pasteurised

Question 18

National control program for salmonella

Answer 18

samples must be taken if you produce eggs for a commercial basis
- only for large scale commercial buisnesses

Flock does not need testing if
- Production is for private domestic use- is not entering the market
- fewer than 350 hens and supplies the consumer direct e.g. farm- gate sales

Question 19

British lion eggs

Answer 19

Code of production of eggs for large consumers
all are vaccinated so eggs are much safer

Question 20

Protection from salmonella

Answer 20

• National control plan
• vaccination
• not sending eggs from salmonella contaminated flocks for class A human consumption