Carl Llor1, Cliodna A M McNulty2, Christopher C Butler3. 1. Institute of Primary Care and Public Health, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK carlesllor@urv.cat. 2. Public Health England Primary Care Unit, Microbiology Department, Gloucestershire Royal Hospital, Gloucester, UK. 3. Institute of Primary Care and Public Health, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK Department of Primary Care Health Sciences, Oxford University, Oxford, UK.