Within the samples, the team 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 other areas that were MRSA and most often resistant to other antibiotics. Studying family trees among the bacteria, they found that the European CC80 clone evolved from the strain from sub-Saharan Africa. They also noted that 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 became resistant to fusidic acid.
The methicillin-sensitive S. aureus resided in sub-Saharan Western Africa, potentially as a result of the local human migration patterns, Stegger said. The investigators hypothesize that CC80 moved to other countries starting in the mid-1980s due to several factors, including increased migration from sub-Saharan Africa in search of better economics, and as a result of an increase in European tourism to this region of Africa, he said. The simultaneous acquisition of methicillin and fusidic acid resistance determinants and their stability in the European CA-MRSA could be a result of a higher selective pressure in North Africa and Europe.
|Contact: Jim Sliwa|
American Society for Microbiology