If you’ve hit your limit with COVID-19 and the threat of monkeypox…you may want to take a seat. There is a new study that has found a strain of the superbug MRSA that is highly resistant to any antibiotics.
MSRA, or methicillin-resistant Staphylococcus aureus, has risen in livestock over the last 50 years. This is most likely due to the widespread use of antibiotics in pig farming.
The strain of MRSA called CC398 now is the dominant type of bug in European livestock, and it has been growing as a means of human infections with MRSA.
According to this new study, CC398 has kept its antibiotic resistance now for decades in pigs and other livestock. They found that it is capable of adapting to a human host very quickly and still maintaining resistance to antibiotics.
According to the experts, this is now a potential threat to public health. It has been found in people who have and have not had direct contact with livestock.
Dr. Gemma Murray is the lead author of the study and she was previously in the University of Cambridge’s Department of Veterinary Medicine and is now at the Wellcome Sanger Institute. She said, “Historically high levels of antibiotic use may have led to the evolution of this highly antibiotic resistant strain of MRSA on pig farms.”
Murray also said that experts found that the antibiotic resistance in this strain of MRSA is very stable and has continued to be a threat for several decades through different livestock species.
Although the CC398 strain has been found in a variety of species, it is most common in pigs. There has been a very noticeable increase in Danish pig farms. The MRSA-positive herds have increased from under 5% in 2008 to 90% in 2018.
Dr. Lucy Weinert is in the University of Cambridge’s Department of Veterinary Medicine and is the senior author of the paper. She said that understanding the way CC398 works in European livestock and the capacity it has to infect humans is “vitally important in managing the risk it poses to public health.”
The viability of infecting humans with CC398 is connected to three mobile genetic elements in the MSRA genome. These elements of genetic material enable MRSA to resist antibiotics and also evade the human immune system.
Two of the genetic elements studied by the researchers included tracing the evolutionary history and its reconstruction. They looked at Tn916 and SCCmec as the elements that enable antibiotic resistance in MRSA. These elements remain stable in pics for decades and stayed stable with transferred to humans. They also carry high levels of resistance to antibiotics that are commonly used on farms.
They also looked at a third mobile genetic element called φSa3. It allows the CC398 strain of MRSA to evade the human immune system. They found that this element allows the CC398 to rapidly adapt to humans.
“Cases of livestock-associated MRSA in humans are still only a small fraction of all MRSA cases in human populations, but the fact that they’re increasing is a worrying sign,” said Weinert.
Increased farming along with high levels of antibiotic use in livestock has increased concerns that livestock is becoming a reservoir of antibiotic-resistant human infections.
For instance, zinc oxide has been used for years in pig farms to prevent diarrhea in piglets. But now the European Union is going to ban the substance due to its environmental impact and the potential of increasing antibiotic resistance in livestock.
Experts indicate that this might not help reduce the increase of CC398 because the genes that induce antibiotic resistance and not necessarily linked to the genes that are induced in the zinc treatment.
The World Health Organization now believes that MRSA is one of the greatest global threats to human health.
