Differences in molecular epidemiology of Staphylococcus aureus and Escherichia coli in nursing home residents and people in unassisted living situations

Abstract

The usefulness of colonization pressure as a working model and proxy for infection transmission is limited due to the inability to grade or quantify the specific risk within environments that are subject to change. To elaborate on the colonization pressure model by comparing the molecular epidemiology of two bacteria, Staphylococcus aureus and Escherichia coli, among residents in a nursing home and people in unassisted living situations. A cross-sectional study of 73 elderly residents from a village in south-central Sweden was conducted. Of these, 35 were residents of a nursing home, and 34 lived in an own place of residence in the same geographical area. Samples of two representative bacterial species were collected from multiple body sites and analysed for molecular diversity. Combining all body sites, 47% of the participants were colonized with S.aureus and 93% with E.coli. The nursing home group, the group in unassisted living situations, and both units combined, held 16, 17, and 29 different S.aureus spa types, respectively. The corresponding numbers of different E.coli serogenotypes were 34, 28, and 48. Diabetes mellitus was associated with more frequent colonization with S.aureus. The molecular diversity of bacteria found within different forms of accommodation was within the same range. Hospital quality hygiene might have contributed to the absence of homogenization of the molecular diversity within the nursing home group. Diabetes mellitus might have played a role in a patient selection characterized by advanced age.