Epistasis mediated by a tRNA synthethase alleviates the cost of antibiotic resistance for MRSA. Staphylococcus aureus

Antibiotic resistance incurs a fitness cost to bacteria which vary between resistance mechanisms. Mupirocin resistance mediated by mutation of the isoleucyl-tRNA synthethase gene has been shown to have little cost to the fitness of the resistant bacteria in vitro. However, this mutation has also been associated with changes in the virulence of the bacteria and decreased expression of toxins, which alleviates the costs associated with mupirocin resistance. Through construction of a suite of mutants the link between increased mupriocin resistance and decreased toxin production was investigated.