MRSA progresses from colonisation to infection in 3 weeks

MRSA progresses from colonisation to infection in 3 weeks

Study shows median time to infection is 22 days, with risk highest in the peri-hospitalisation period.

A new retrospective cohort study published in BMC Infectious Diseases has looked at 909 patients known to have newly identified MRSA colonisation during admission to National University Hospital, Singapore, to determine the circumstances under which acquisition of MRSA becomes infection. Patients with previous history MRSA colonisation or infection and those who had been a hospital inpatient in the preceding 12 months were excluded.

Of the 121 patients (14.4%) who developed MRSA infection, 40.5% of those (49 patients) were infected in skin and soft tissue, and 11.6% (14) in bones and joints – which may be of concern to wound care providers, eg when a pressure ulcer forms over a bony prominence. Seven of 13 patients who had bacteraemias were secondary to infection at other sites.

“The study shows that the highest risk for MRSA infection occurs shortly after patients become colonised,” write the authors. “However, a significant proportion of these patients will present with their infection in a different admission to that in which they became colonised.”

These results may demonstrate that wound care clinicians need to be alert for the presence of MRSA, and to take action – eg applying topical antimicrobials to wounds – in the early states of colonisation.

“Targeting interventions such as decolonisation therapy and enhanced efforts to prevent device-associated infection to reduce development of infection in patients who newly acquire MRSA colonisation may … have a key role," add the authors. "Since most infections occur soon after colonisation, useful further work would include the study of immune mechanisms that may offer partial longer-term protection including potentially prophylactic or therapeutic vaccines."

Read the full study here.