The Gram-positive bacterium Staphylococcus aureus is a human bacterial pathogen causing many nosocomial infections from skin lesions to life-threatening diseases such as bacteraemia, pneumo- nia, endocarditis, osteomyelitis, toxic shock syndrome, and septicaemia [1]. Treatment of these diseases has become more difficult and more expensive because of the increasing prevalence of multiresistant strains, especially methicillin-resistant S. aureus (MRSA) in recent decades. However, because MRSA increases morbidity and costs of treatment of patients compared with infections caused by methicillin-susceptible S. aureus (MSSA), many hospitals have attempted to control the spread of the former pathogen.