How this gecko found its way into this egg remains a mystery. (Jack Kerr)

The Northern Territory president of the Australian Medical Association says he may have accidentally discovered how the potentially deadly salmonella bacteria gets inside chicken eggs.

Dr Peter Beaumont was cooking when he discovered a dead gecko between the inner shell and the membrane of a chicken egg he cracked open.

He believes the discovery is a world first and has handed the egg shell over to health authorities who will look for the presence of bacteria in the yolk and try to work out how the gecko got into the egg.

Dr Beaumont says he suspects the gecko entered the chicken before it entered the egg.

"Eggs are made inside chooks up this tube from their bottom.

"Now obviously this tube is in contact with the whole outside world.

"It has to be that the gecko climbed up inside the chook and died up there while the egg was being formed before the shell was put on it."