As has been reported here, SA is carried on our bodies. If you find SA in food you know that the food was contaminated by direct contact with humans.
The organisms is very hardy. It lives on the skin so it is able to grow in the presence of about 10% salt solution. When growing in the body some strains produce enzymes that result in a protective layer being laid down around the bacterial cells. The protective layer helps repel antibiotics making it more difficult to kill in places such bone infection and in udders or mammary glands.
The resistance factors are often associated with small pieces of DNA known as plasmids. Those plasmids can be transferred to other organisms.
