New type of MRSA in hospitalized patients probably of animal origin

June 2, 2011

A distinctly new type of methicillin resistant Staphylococcus aureus (MRSA) that is not detected by traditional genetic screening methods has been discovered in patients in Irish hospitals according to research to be published in the journal Antimicrobial Agents and Chemotherapy. These findings provide significant insights into how new MRSA strains emerge and highlight the potential for the transmission of infectious agents from animals to humans.

MRSA is a significant cause of hospital- and community-acquired infection worldwide. MRSA strains are characterized by the presence of a mobile DNA cassette (known as SCCmec) encoding genes that confer resistance to beta-lactam antibiotics including methicillin and recombinase genes that allow the cassette to transfer into methicillin-susceptible S. aureus (MSSA).

Scientists at the University of Dublin, the Irish National MRSA Reference Laboratory and the University of Dresden and Alere Technologies in Germany identified the new MRSA strain using high throughput screening. Complete genome sequencing revealed that this strain is distinctly different to previously described MRSA. It carries a new type of SCCmec encoding highly divergent genes that are very different to any described previously in MRSA or in any other organism. Consequently the new strain is not detected as MRSA by routine conventional and real time DNA-based (PCR) assays commonly used to screen patients for MRSA. The MRSA strain was found to belong to the genetic lineage clonal complex 130 (CC130), which has previously only been associated with MSSA from cows and other animals, but not humans, strongly suggesting that the new MRSA originated in animals.

During the publication process, the authors became aware that a consortium of researchers lead by the University of Cambridge and the Wellcome Trust Sanger Institute in the United Kingdom had identified bovine MRSA with an almost identical SCCmec element to that in the Irish CC130 human MRSA. These researchers also identified MRSA harboring the novel SCCmec element emerging in bovine and human populations in the United Kingdom and Denmark. This study will be published simultaneously in Lancet Infectious Diseases.

Commenting on the significance of the findings, Professor David Coleman from the University of Dublin said: "The results of our study and the independent United Kingdom study indicate that new types of MRSA that can colonize and infect humans are currently emerging from animal reservoirs in Ireland and Europe and it is difficult to correctly identify them as MRSA. This knowledge will enable us to rapidly adapt existing genetic MRSA detection tests, but has also provided invaluable insights into the evolution and origins of MRSA."

Explore further: Study finds fire stations contaminated with MRSA

More information: Anna C. Shore, Emily C. Deasy, Peter Slickers, Grainne Brennan, Brian O'Connell, Stefan Monecke, Ralf Ehricht, and David C. Coleman. Detection of Staphylococcal Cassette Chromosome mec Type XI Encoding Highly Divergent mecA, mecI, mecR1, blaZ and ccr Genes in Human Clinical Clonal Complex 130 Methicillin-Resistant Staphylococcus aureus. Antimicrobial Agents and Chemotherapy, published ahead of print on 2 June 2011, doi:10.1128/AAC.00187-11

Meticillin-resistant Staphylococcus aureus with a novel mecA homologue emerging in human and bovine populations in the UK and Denmark: a descriptive study. The Lancet Infectious Diseases, Online First publication, published Online June 3, 2011 DOI:10.1016/S1473-3099(11)70126-8

Related Stories

Study finds fire stations contaminated with MRSA

June 1, 2011
MRSA transmission may be occurring in fire stations, according to a study published in the June issue of the American Journal of Infection Control, the official publication of APIC – the Association for Professionals ...

Recommended for you

Co-infection with two common gut pathogens worsens malnutrition in mice

July 27, 2017
Two gut pathogens commonly found in malnourished children combine to worsen malnutrition and impair growth in laboratory mice, according to new research published in PLOS Pathogens.

Finish your antibiotics course? Maybe not, experts say

July 27, 2017
British disease experts on Thursday suggested doing away with the "incorrect" advice to always finish a course of antibiotics, saying the approach was fuelling the spread of drug resistance.

Phase 3 trial confirms superiority of tocilizumab to steroids for giant cell arteritis

July 26, 2017
A phase 3 clinical trial has confirmed that regular treatment with tocilizumab, an inhibitor of interleukin-6, successfully reduced both symptoms of and the need for high-dose steroid treatment for giant cell arteritis, the ...

A large-scale 'germ trap' solution for hospitals

July 26, 2017
When an infectious airborne illness strikes, some hospitals use negative pressure rooms to isolate and treat patients. These rooms use ventilation controls to keep germ-filled air contained rather than letting it circulate ...

Researchers report new system to study chronic hepatitis B

July 25, 2017
Scientists from Princeton University's Department of Molecular Biology have successfully tested a cell-culture system that will allow researchers to perform laboratory-based studies of long-term hepatitis B virus (HBV) infections. ...

Male hepatitis B patients suffer worse liver ailments, regardless of lifestyle

July 25, 2017
Why men with hepatitis B remain more than twice as likely to develop severe liver disease than women remains a mystery, even after a study led by a recent Drexel University graduate took lifestyle choices and environments ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.