Abstract: The invention provides a method of inhibiting production of bacteria which constitutively express PBP2' or bacteria which inducibly express PBP2' in the presence of a .beta.-lactam antibiotic, by administering an effective amount of an extract of tea to the bacteria. The tea extract contains at least one active principle of dried tea and being extractable from processed dried tea with hot water and this active principle is capable, on administration, of restoring the activity against methicillin-resistant Staphylococcus aureus (MRSA) of a .beta.-lactam antibiotic. Preferably, the extract of tea can be administered to a human or animal subject together with a .beta.-lactam antibiotic.