Genomic analysis, a faster approach to infection detection

MRSA Photo credits: The University of Chicago Medicine

MRSA
Photo credits: The University of Chicago Medicine

A recent methicillin-resistant staphylococcus aureus (MRSA) outbreak in was detected and traced to origin quicker than conventional means thanks to genomic sequencing. A special care baby unit (SCBU) in Cambridge, UK was persistently infected with a new type of MRSA, (ST) 2371. However, a research group of the United Kingdom was able to link independent MRSA cases and find original carrier of the strain to stop further infection.

MRSA is a staphylococcus bacterium that has become resistant over time to the traditional narrow-spectrum antibiotic methicillin, the usual killer of staph bugs. Although not particularly harmful to healthy adults, MRSA can prove life threatening in those with compromised or underdeveloped immune systems such as hospital inpatients.

MRSA was detected initially in this SCBU through conventional epidemiological data and antibiogram profiles by the infection-control team. However, it wasn’t until genomic sequencing of isolated MRSA bacterium and carrier DNA, was the germ able to be tracked back to linked carriers and originator of the outbreak. 12 infants were found to be MRSA colonized over a 6-month period, and 11 of the cases proved to be genetically linked. After initial detection, the unit underwent deep cleaning. However, four days post-cleaning another infant of the unit was found as MRSA colonized. This led to the assumption of a staff staph carrier.

MRSA screening of all 154 staff members led to the detection of MRSA on one staff member through their genomic infection profile. This was the originator of the persisting infection.

Early sequencing may have detected the MRSA outbreak sooner. As genomic sequencing becomes more commonplace compared to its 1976 inception, infectious outbreaks such as this may be stopped before they spread. The authors of the research article may have said it best, “Whole-genome sequencing holds great promise for rapid, accurate, and comprehensive identification of bacterial transmission pathways in hospital and community settings, with concomitant reductions in infections, morbidity, and costs.”

Reference:
Simon R. Harris, Edward J.P. Cartwright, M. Estée Török, Matthew T.G. Holden, Nicholas M. Brown, Amanda L. Ogilvy-Stuart, Matthew J. Ellington, Michael A. Quail, Stephen D. Bentley, Julian Parkhill, Sharon J. Peacock. 2012. Whole-genome sequencing for analysis of an outbreak of meticillin-resistant Staphylococcus aureus: a descriptive study. The Lancet Infectious Diseases.
http://www.thelancet.com/journals/laninf/article/PIIS1473-3099(12)70268-2/fulltext

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