Widespread antibiotic use in pig farming may be to blame for the emergence of a highly antibiotic-resistant strain of the superbug MRSA in livestock in the last 50 years.
The dominant type of MRSA in European livestock has been called CC398. Human MRSA infections are caused by it.
Over the course of decades, the study found that CC398 has maintained its resistance to antibiotics. It is able to quickly adapt to humans while maintaining resistance to antibiotics.
This strain of MRSA could pose a threat to public health. Increasing numbers of human infections have been associated with it.
The evolution of a highly antibiotic resistant strain of MRSA may have been caused by high levels of antibiotic use on pig farms.
She said that the antibiotic resistance in this livestock-associated MRSA is stable and that it has been around for many decades.
The use of antibiotics in Europe is lower than it has been in the past. Reductions in antibiotic use on pig farms are likely to have a limited impact on the presence of this strain of MRSA in pigs.
CC398 is most often associated with pigs and is found across a wide range of livestock species. The proportion of pig farms with MRSA-positive herds has increased from less than 5% in 2008 to more than 90% in the last 10 years. There is no MRSA in pigs.
The emergence and success of CC398 in European livestock is important in managing the risk it poses to public health.
Three mobile genetic elements in the MRSA genome are related to the success of CC398 in livestock. There are chunks of genetic material that give the MRSA certain characteristics.
The evolutionary history of two mobile genetic elements called Tn 916 and SCC mec that confer antibiotic resistance in MRSA has been reconstructed by the researchers. When CC398 jumps to humans, they carry with them high levels of resistance to antibiotics used in farming.
A third mobile genetic element called Sa3 was found to have frequently disappeared and reappeared in both human-associated and livestock-associated CC398. It is suggested that CC398 can quickly adapt to humans.
Cases of livestock-associated MRSA in humans are still a small fraction of all MRSA cases in human populations, but the fact that they're increasing is worrying.
Increased farming and high levels of antibiotic use in livestock have led to concerns about human infections becoming resistant to antibiotics.
Pig farms have used zinc oxide for a long time. The European Union will ban its use from this month due to concerns about its impact on the environment. The genes that confer resistance to zinc treatment are not always linked to the genes that confer resistance to antibiotics.
In 1960, MRSA was identified in humans. It is more difficult to treat due to its resistance to antibiotics. One of the greatest threats to human health is MRSA.
Today's findings are published in the journal e Life.
More information: Marta Matuszewska et al, Stable antibiotic resistance and rapid human adaptation in livestock-associated MRSA, eLife (2022). DOI: 10.7554/eLife.74819 Journal information: eLife
All Rights Reserved © 2024
