ampicillin resistance in Staphylococcus aureus - (Jan/09/2006 )

hi! i am working with a wild type strain of Staphylococcus aureus,which does not has a mec A gene,which is thought to be responsible for ampicillin resistance, neither does it have any chance of aquiring mec A, from any other source. Yet, it is repeatedly showing resistance to ampicillin. Is there any other mechanism for developement of ampicillin reistance in S. aureus?

what concentration of amp? completely resistant, or is the growth pukey and slow?

methicillin resistance and resistance to beta-lactams is not always synonymous