The Importance of Environmental Screening in a Methicillin-Resistant Staphylococcus aureus (MRSA) Outbreak Investigation in a Transplant Unit

Abstract

Background: Methicillin-resistant Staphylococcus aureus (MRSA) colonization conveys a higher risk of invasive infection. The transplant cohort is a group of immunocompromised patients who are at higher risk of infection. We conducted an outbreak investigation of hospital-acquired MRSA colonization within the transplant unit, which led to the discovery of positive isolates within our environment and to changes in our hospital disinfection policies. Methods: Our transplant unit consists of 8 single, positive-pressure rooms housed separately at the side of a larger ward. Staffing from this unit differs from the rest of the shared ward that houses up to 60 patients. As part of hospital screening, we found that a patient admitted for a stem-cell transplant had acquired nosocomial MRSA colonization. Given the unusual occurrence of such an event, a root-cause analysis was conducted. Results: A meeting was convened together with nursing, medical staff, and ancillary staff. Identified areas of potential transmission were deemed equipment, staff, and patients, and screening was performed. Shared equipment included the portable electrocardiogram (ECG) machines and portable x-ray machines and boards. In particular, ECG machines were shared with the adjoining nontransplant oncology ward. The usual practice was to clean the machine after use but not prior to the next use. This was deemed a possible exposure risk in view of a recent MRSA outbreak in a separate section of the ward. Positive isolates were found on both the x-ray and ECG machines. All healthcare workers were screened and were negative for MRSA. Furthermore, 7 patients admitted during the same time period were also screened for MRSA and were negative. Given the concurrent outbreak within the ward, pulsed-field gel electrophoresis was performed for all MRSA isolates obtained and the outbreak strain. These were found to be nonclonal (Table 1). Work processes for both the cleaning of ECG and x-ray machines were enhanced and modified. Hand hygiene measures to ward and radiology staff were reinforced. Thus far, no further cases have been detected. Conclusions: The environment is an important part of outbreak investigation. Shared equipment is often overlooked during day to day processes but should not be neglected. This can result in changes to hospital disinfection policy.

Funding: None

Disclosures: Indumathi Venkatachalam reports receiving honoraria for speaking engagements for bioMérieux and Pfizer and serving on an expert panel for MSD Pharma.