Detection of Methicillin-Resistant Staphylococcus aureus Nasal Carriage Among Hospital Staff

Abstract

Nurses, doctors, laboratory staff and cleaners work in close contact with patients who carry methicillin-resistant Staphylococcus aureus (MRSA), and a nose swab from a member of staff is one of the simplest tests in hospital infection control. This narrative review asks what such a swab can and cannot tell us. It draws on published work on the biology of nasal carriage, the origin and spread of MRSA lineages, the part played by healthcare workers in transmission, and the laboratory methods used to detect carriage, and it reports no new data and no results from any single hospital. Carriage is common in staff as in the general population, but it is a dynamic state rather than a fixed trait, and a positive swab is better read as a marker of exposure and possible risk than as evidence that a person has passed the organism on. Reported carriage depends heavily on where the swab is taken, how it is cultured and how methicillin resistance is confirmed, so figures from different studies are seldom comparable. Screening of staff is best reserved for situations in which transmission is already linked to them. The review closes with the reporting items that a credible carriage study should supply.