1900: Staphylococcus aureus causes fatal bacterial infections in humans. No antibiotics available. 1945: Penicillin kills almost all Staphylococcus aureus. 1970s: About 95 per cent of the bacteria becomes resistant to penicillin. The new genes produce an enzyme called penicillinase which destroys penicillin. New strain: Penicillin-resistant Staphylococcus aureus (PRSA). 1980s: New antibiotics methicillin and cloxacillin kill 99 per cent of bacteria. 1990s: Thirty per cent of bacteria found to be resistant to methicillin and cloxacillin. Killed by antibiotic of last defence, vancomycin. New strain: Methicillin-resistant Staphylococcus aureus (MRSA). 1997: Japan discovers bacteria resistant to vancomycin, following three cases in the United States and also one in France. New strain: Vancomycin-resistant Staphylococcus aureus (VRSA). 1998: Hong Kong reports first VRSA case. Woman dies in public hospital after two-week antibiotics treatment failed. 1999: Two more patients are found to have died at same public hospital and another at a second hospital.