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."

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

Experimental MERS vaccine shows promise in animal studies

July 28, 2015

A two-step regimen of experimental vaccines against Middle East respiratory syndrome (MERS) prompted immune responses in mice and rhesus macaques, report National Institutes of Health scientists who designed the vaccines. ...

Can social isolation fuel epidemics?

July 21, 2015

Conventional wisdom has it that the more people stay within their own social groups and avoid others, the less likely it is small disease outbreaks turn into full-blown epidemics. But the conventional wisdom is wrong, according ...

Lack of knowledge on animal disease leaves humans at risk

July 20, 2015

Researchers from the University of Sydney have painted the most detailed picture to date of major infectious diseases shared between wildlife and livestock, and found a huge gap in knowledge about diseases which could spread ...

IBD genetically similar in Europeans and non-Europeans

July 20, 2015

The first genetic study of inflammatory bowel disease (IBD) to include individuals from diverse populations has shown that the regions of the genome underlying the disease are consistent around the world. This study, conducted ...

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.