In reply to Pesda potato:
However, outbreaks of salmonellosis (an infection caused by Salmonella bacteria) still happen because Salmonella also silently infects the ovaries of healthy-looking hens, contaminating the eggs inside the chicken before the shells are even formed, according to FSIS.18 Aug 2010
How Does Salmonella Get Inside Eggs? - LiveScience
www.livescience.com/10016-salmonella-eggs.html
https://www.google.co.uk/search?q=salmonella+inside+eggs