Antibiotics are commonly used to treat infections, but they may also affect how other infections are detected and transmitted. MRSA is a potentially serious healthcare-associated infection. Over the past decade there has been major progress in reducing the number of patients who carry MRSA on their skin and other body sites, and in reducing infections due to MRSA. We plan to use mathematical models to investigate how antibiotic use in affects the transmission of MRSA. Using data from the Oxford adult intensive care unit, for several different antibiotics, we will consider the effect of each antibiotic on detection of MRSA by screening tests (nose swabs), susceptibility to acquisition of MRSA carriage, and the chance of onward transmission from known carriers.