Factors affecting methicillin resistance in Staphylococcus aureus.

Methicillin resistance in staphylococci is primarily due to the methicillin resistance determinant which produces an additional low affinity penicillin-binding protein PBP2'. Expression of PBP2' is controlled by its own regulatory element, and shares also the same induction system as beta-lactamases. However, methicillin resistance levels do not correlate with the amount of PBP2' produced, but are determined by the strain specific genetic background. These factors responsible for high methicillin resistance have not yet been characterised.