Washington, Aug 26 (IANS): Scientists have found that the predominant strain of community-associated, methicillin-resistant Staphylococcus Aureus (CA-MRSA) was derived from a single sub-Saharan ancestor.

The virus infects healthy people and the infections may be transmitted through close person-to-person contact or contact with a contaminated item like a towel or clothing.

People in Europe, the Middle East and northern Africa have been the main victims of the virus.

"With increasing levels of CA-MRSA reported from most parts of the Western world, there is a great interest in understanding the origin and factors associated with the emergence of these epidemic lineages," said Marc Stegger from the department of microbiology at the Statens Serum Institut in Denmark.

The study determined that a single descendant of a methicillin sensitive ancestor circulating in sub-Saharan Africa rose to become the dominant CA-MRSA clone in Europe, the Middle East and north Africa.

For this, the team analyzed 97 SA samples from 22 countries in Europe, North Africa, sub-Saharan Africa, the Middle East and Asia isolated between 1993 and 2010.

It was found that 23 samples were sensitive to methicillin while 74 were resistant to methicillin.

Within the samples, they identified two distinct groups of S. Aureus: a methicillin-sensitive clone from sub-Saharan Africa that was susceptible to all antibiotics, and the rest from all the other areas that were MRSA and most often resistant to other antibiotics.

In the transition from a methicillin-sensitive line to a CA-MRSA clone, the bacteria simultaneously acquired two highly specific genetic elements making them resistant to methicillin and fusidic acid, noted the team.

The strain moved to other countries starting in the mid-1980s due to increased migration from sub-Saharan Africa, said the study that appeared in mBio, the online journal of American Society for Microbiology.