This article only describes one highly specialized aspect of its associated subject. Please help improve this article by adding more general information. The talk page may contain suggestions.(October 2009)
Penicillin resistance in Staphylococcus aureus appeared very soon after penicillin entered general clinical use in 1943, and the mechanism of resistance was the production of β-lactamase. Modifications of the penicillin molecule so that it was resistant to being broken down by β-lactamase was able to temporarily overcome this problems: these compounds became known as antistaphylococcal penicillins. The first of these compounds was methicillin, which is no longer in general use. The range of these penicillins available in each country is very different, and the reasons for this are historical.