2 April 2013

3 minute read

The study Whole genome sequencing identifies zoonotic transmission of MRSA isolates with the novel mecA homologue mecC from researchers at Cambrisge University in the UK, the Wellcome Trust Sanger Institute, Statens Serum Institut in Denmark, the Department of Clinical Microbiology, Slagelse Sygehus, Denmark and the Moredun Research Institute in the UK said the research also shows the potential of whole genome sequencing in epidemiological investigations and source tracking of bacterial infections.

The results of the work by Ewan M. Harrison, Gavin K. Paterson, Matthew T.G. Holden, Jesper Larsen, Marc Stegger, Anders Rhod Larsen, Andreas Petersen, Robert L. Skov, Judit Marta Christensen, Anne Bak Zeuthen, Ole Heltberg, Simon R. Harris, Ruth N. Zadoks, Julian Parkhill, Sharon J. Peacock and Mark A. Holmes is published in the journal EMBO Molecular Medicine.

In the US, campaigning congresswoman Louise Slaughter has welcomed the research and has called on the US authorities to react by reducing the use of antibiotics in livestock.

In the study, the researchers said that several methicillin-resistant Staphylococcus aureus (MRSA) lineages that carry a novel mecA homologue (mecC) have recently been described in livestock and humans.

In Denmark, two independent human cases of mecC-MRSA infection have been linked to a livestock reservoir.

"We investigated the molecular epidemiology of the associated MRSA isolates using whole genome sequencing (WGS)," the researchers said.

"Single nucleotide polymorphisms (SNP) were defined and compared to a reference genome to place the isolates into a phylogenetic context.

"Phylogenetic analysis revealed two distinct farm-specific clusters comprising isolates from the human case and their own livestock, whereas human and animal isolates from the same farm only differed by a small number of SNPs, which supports the likelihood of zoonotic transmission."

Further analyses identified a number of genes and mutations that may be associated with host interaction and virulence.

"This study demonstrates that mecC-MRSA ST130 isolates are capable of transmission between animals and humans, and underscores the potential of WGS in epidemiological investigations and source tracking of bacterial infections," the research team said.

Congresswoman Slaughter said that "the groundbreaking study was conducted by genetics researchers who analysed the genomes of MRSA bacteria from patients and their farm animals, and found the samples to be genetically identical".

In reaction, she has sent a letter to Dr Margaret Hamburg, the Commissioner of the US Food and Drug Administration calling for immediate action to reduce the use of antibiotics in livestock.

In sending the letter, Congresswoman Slaughter said: "This study ends any debate. The extreme overuse of antibiotics in livestock is endangering human health."

Congresswoman Slaughter added: "For decades, the United States Food and Drug Administration has failed to act in the face of a growing threat. These findings make it clearer than ever that their failure is endangering human life. Starting today, the FDA must take strong federal action to reduce antibiotic use in livestock and protect human health."

She said that the findings come on the heels of public health warnings in the United Kingdom and the United States about the catastrophic threat of antibiotic disease.

Earlier this month, Dr. Tom Frieden, director of the US Centers for Disease Control, warned that "our strongest antibiotics don't work and patients are left with potentially untreatable infections," the congresswoman said.

Further Reading You can view the full report by clicking here.

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