In this paper we will consider the question of mutation as it is manifested in press coverage of MRSA in UK hospitals. This represents a fertile field of discourse which brings into focus issues relating to microbes, people and working practices as well as the concepts of risk and vulnerability. A regular feature of reporting has been the presence of explanations for drug resistance involving repeated random mutations of the microbe to achieve progressively greater resistance and versatility, largely through a Darwinian process which is ‘clever’ at overcoming human attempts at elimination. More recently a discourse has emerged which foregrounds also the vulnerability of patients who are very young, old or otherwise immunocompromised, or whose own genetic makeup might put them at risk from the microbe. The hospital is decentred as a source of infection, and attention is turned instead to nursing homes and gymnasia as sources of infection in the community. This latter development mitigates the responsibilities of hospitals and statutory healthcare providers and turns the risk back towards the individual as a responsible actor in an ecology of mutation.