Although our retrospective study has some limitations (i.e. relatively low numbers of isolates and patients, or non-matched sampling times), the results show that not only the PR3-ANCA-AAV patients, but also the MPO-ANCA-AAV patients mainly carry S. aureus types that are carried in the general population. The gene discussed is MPO; the disease is anti-neutrophil cytoplasmic antibody-associated vasculitis.