Mupirocin is a naturally occurring antibiotic. This antibacterial agent is produced by fermentation using the organism Pseudomonas fluorescens. It is active against a wide range of bacteria (e.g. Staphylococcus aureus including methicillin-resistant strains and Streptococcus pyogenes) those responsible for the majority of skin infections. It is also active against gram-negative pathogens, such as Escherichia coli and Haemophilus influenzae. Mupirocin inhibits bacterial protein synthesis by reversibly and specifically binding to bacterial isoleucyl transfer-RNA synthetase.