Nottingham Staphylococcus aureus population study: prevalence of MRSA among elderly people in the community

Abstract

We used electoral ward level statistics from 1991 to combine the catchment areas of seven large general practices and provide a study population of which the demographic composition (age, sex, social class, ethnicity, and proportion of elderly people living alone) was representative of the Nottingham Health District, which in most respects is similar to England as a whole.4 With the general practitioners' cooperation, we invited 1615 randomly selected people aged 65 or over to take part in the study, excluding those whose permanent address was a residential or nursing home. We carried out the study at the time of administration of influenza vaccinations on the premises of the participating surgeries. Of those invited, 1047 (64.8%) elderly people presented for the investigation, and we enrolled 962 into the study. Samples consisted of swabs taken from both anterior nares. We used standard laboratory protocols to enrich and identify methicillin susceptible S aureus and MRSA and used SmaI macrorestriction to type them genetically. We collected data on baseline demographic variables as well as specific risk factors. We used the χ² test for univariate analysis of categorical variables, multivariate logistic regression to identify independent risk factors, and ward based Jarman deprivation scores to stratify data by socioeconomic characteristics.5