Super-bacteria tracked
2010-01-22 11:26
Washington - Scientists have succeeded in tracking the patient-to-patient transmission of the multi-drug resistant MRSA bacteria, which they hope will allow for better control and prevention of the dreaded superbug.
For the first time, researchers have determined how MRSA, or methicillin-resistant staphylococcus aureus - a type of staph skin infection, spreads from one person to another, particularly in hospitals - the setting where the bacteria often proliferates.
"The ability to track strains in this way will enable researchers to understand how strains can spread so rapidly, and should lead to novel infection control strategies - not only for MRSA but also for other emerging superbugs," said a statement from the Wellcome Trust Sanger Institute in Britain, which conducted the study in co-operation with the University of Bath.
Scientists used sophisticated DNA sequencing technologies to compare individual MRSA samples from patients to precisely show how closely related they were genetically.
The study was able to identify incremental changes in the genetic code and to identify differences between even the most closely-related of MRSA specimens.
Health challenge
The super-bug's resistance to treatment has created a major health challenge, particularly in the hospital setting where it often proliferates.
Stephen Bentley, the senior author on the paper, said the study allows researchers and public health officials to determine how infections spread "from person to person, from hospital to hospital, from country to country".
The study took one set of 42 samples taken from people across the globe who became infected with MRSA between 1982 and 2003.
A second set of samples came from a single hospital in northeast Thailand, and consists of 20 probes from patients who had developed MRSA infection within seven months of each other - all possibly linked by a person-to-person transmission.
The team sequenced the entire genomes of all the samples using cutting-edge DNA sequencing technology, which was able to reveal minute genetic changes, and showed that no two infections were caused by entirely identical bacteria.
Having identified the subtle genetic differences, the researchers divided the Thai hospital samples into two groups and found five that were extremely similar.
"This group of five related MRSA strains caused infections in patients who were resident in intensive care units in adjacent blocks of the hospital," explained Ed Feil, from the Department of Biology and Biochemistry at the University of Bath, and one of the main authors on the study.
Life-threatening infections
"Bacteria from patients housed in other parts of the hospital were much less similar," he said.
To better understand better the evolution and spread of MRSA over several decades and large geographic distances, the team also looked at samples from hospitals in North and South America, Europe, Australia and Asia collected over a period of more than two decades.
MRSA usually starts as an outbreak of small red bumps that can quickly turn into deep, painful abscesses requiring surgical draining.
While the bacteria sometimes remains confined to the skin, it can also penetrate the body, causing potentially life-threatening infections in the bones, joints, surgical wounds, heart or lungs.
MRSA shot to prominence in recent years as many people catch the bug while being treated in hospitals - leading to health officials to ban doctor from wearing their traditional white coats in favour of plastic aprons in a bid to reduce the risks of transmission.
In the US, MRSA is the cause of more than 60% of all hospital infections. According to the Centres for Disease Control and Preventions, MRSA in 2005 infected 94 000 people and killed 19 000 in the US.
- SAPA