Proactive WGS Offers a Cost-Effective Tool for MRSA Infection Control

In the fight against methicillin-resistant Staphylococcus aureus (MRSA), investigators in the United Kingdom say that genomic surveillance of MRSA is likely to be a cost-effective intervention for infection control.

According to Public Health England, there were 846 reported cases of bacteremia from MRSA in England from April 1, 2017, to March 31, 2018. That was up from the 825 MRSA bacteremia cases reported from 2016-2017, although there was an 81% drop overall from the 4451 cases reported between 2007 and 2008. Although hospital-onset MRSA cases have fallen in England, the investigators on a new study published in the journal Clinical Infectious Diseases say that while genomic sequencing of MRSA in hospital settings creates an upfront cost, it may help prevent nosocomial MRSA cases, as well as related deaths.

“Whole genome sequencing represents a major advance in the control of multidrug-resistant organisms that spread between patients, units, and facilities,” the investigators wrote. “When combined with patient movement data, this provides a more accurate determination of transmission events and outbreak status than standard infection control methods alone.”

In their paper, the authors point to prior evidence supporting the potential benefits of a “sequence first” infection control approach, which comes from a study of genomic surveillance of MRSA isolated in a large clinical microbiology laboratory in England. That study identified hundreds of transmission clusters not detected by standard infection control, providing early outbreak detection and opportunities to minimize further transmission.

Investigators used a model to estimate the cost-effectiveness of whole genome sequencing of MRSA in combination with standard infection control practice in comparison with standard practice alone. Using a decision-tree framework, the study team estimated the reduction in the total number of MRSA acquisitions along with the cost-effectiveness of whole genome sequencing over 1 year based on an annual cohort of newly admitted hospitalized patients. In the model, patients were classified as either MRSA negative, uninfected MRSA carriers, or symptomatic MRSA infected. In addition, investigators used prior inpatient sample data on MRSA-related hospitalizations to assume that 4.6% of all symptomatic infected MRSA inpatients (involving any site or organ) die of MRSA-related causes before hospital discharge.

With the assumption that data from whole genome sequencing would result in a 90% reduction in MRSA acquisition, the study team ran 65,000 patients through the model and found that genomic sequencing led to 290 fewer new MRSA cases (including both asymptomatic carriage and clinical infection), reducing new MRSA cases by 28.8% and avoiding 2 MRSA-related deaths.

“Our model is the first to estimate the cost-effectiveness of routine whole genome sequencing of MRSA as an infection control tool,” the investigators conclude. “This indicated that routine MRSA sequencing would result in fewer MRSA cases and have a small positive impact on health-related quality of life on a per-patient basis (regardless of whether they have, or are tested for MRSA). This technological application is also likely to be cost saving assuming the relative reduction in MRSA cases is 90%.”

The investigators add that the extent to which sequencing is cost-effectiveness depends upon the prevalence of MRSA colonization in patients upon admission to hospital, and that the potential for reducing MRSA transmission is larger when MRSA colonization is more prevalent.