Staphylococcus aureus Genome sequencing and assembly

Topically applied antibiotic skin creams containing mupirocin and fusidic acid are commonly used in the prevention and treatment of skin infections, particularly those caused by staphylococci. New Zealand has some of the highest rates of topical antibiotic usage and antibiotic resistance in the developed world. Here, we examine multilocus sequence type 1 (ST1) Staphylococcus aureus in NZ within a Bayesian phylogenomic framework and demonstrate a strong association between the clinical introduction of these topical antibiotics and the emergence of MDR ST1 S. aureus. We provide experimental evidence showing that exposure to topical antibiotics can lead to rapid co-selection of MDR S. aureus isolates, resistant to an array of antibiotics, from within a population of “fitter” and non-resistant strains. These findings have important implications relating to the indiscriminate use of topical antibiotics, which should now come under the same clinical scrutiny as more tightly regulated systemic antimicrobials, and should act as a warning to other countries that have recently introduced fusidic acid into clinical use.