An outbreak of livestock-associated meticillin-resistant Staphylococcus aureus (LA-MRSA) clonal complex 398 in a regional burns centre

Abstract

Background: Meticillin-resistant Staphylococcus aureus (MRSA) outbreaks have been reported previously in burns centres with resulting mortality and morbidity. This article describes the first human-associated outbreak in the UK caused by a strain of mupirocin-resistant (MuR) livestock-associated MRSA clonal complex 398 (LA-MRSA CC398) in an adult burns centre. The centre historically had a very low prevalence of MRSA infections.

Aim: To describe the clinical and epidemiological context of how the outbreak was identified and contained using a range of infection prevention and control (IPC) measures guided by both traditional and genetic methods.

Methods: A cluster of MuR-MRSA led to an outbreak investigation. Cases were detected via retrospective search and real-time laboratory surveillance. Isolates were sent continuously for whole-genome sequencing (WGS). A live timeline of cases and interventions was produced throughout the period.

Findings: The outbreak consisted of 12 cases (seven males and five females) aged between 22 and 70 years. Patients were identified between May and October 2020. All patients were colonized rather than infected. The strain acquired the plasmid bearing MupA while colonizing the index case before dissemination. The index case was found to be a chicken farmer. This outbreak was eventually controlled using IPC measures, audits, and blind staff decolonization guided by insight from WGS.

Conclusion: It was not possible to determine how the strain entered the centre, or if a staff carrier was involved. The outbreak demonstrated the potential for continued transmissions for months despite active surveillance and stringent control measures.

Keywords: Burns; CC398; Chlorhexidine resistance; LA-MRSA; Mupirocin resistance; Outbreak.