Super germ caused by antibiotics in pig farming
Over the past 50 years, pigs have developed a superbug called methicillin-resistant Staphylococcus aureus, or MRSA for short. The pathogen, most likely caused by the widespread use of antibiotics in pig farming, is increasingly becoming the cause of MRSA infections in humans, according to a recent study.
In a recent study, researchers from the University of Cambridge (England) showed that a highly antibiotic-resistant strain of MRSA called CC398 from pigs can spread to humans. The superbug poses a potential threat to public health, the team warns in the journal eLife.
A potential threat to human health
MRSA infection was first detected in a human patient in 1960. Due to antibiotic resistance, the infection is much more difficult to treat than other bacterial infections. The World Health Organization (WHO) considers MRSA to be one of the greatest threats to human health worldwide.
How does an MRSA infection manifest?
Many people carry MRSA pathogens on their skin, for example, but do not develop any symptoms as a result. Infectious diseases can only be triggered when bacteria enter the body through wounds or mucous membranes. Possible symptoms include:
MRSA risk groups
MRSA is one of the typical hospital germs. People who are hospitalized, living in a rest home or dependent on dialysis are therefore particularly at risk.
People with diabetes, people with weakened immune systems, and the elderly and infants are also at increased risk of serious MRSA infections.
Antibiotic resistance developed in pig farming
Strains of Staphylococcus bacteria with the designation CC398 are characterized by particularly high resistance to antibiotics. The bacterial strain has evolved in pigs raised as livestock over the past five decades.
The Cambridge University working group has just proved that resistant bacteria can also adapt to humans while retaining the resistance to antibiotics acquired in pigs.
The results of the study highlight the potential threat that this strain of MRSA poses to public health. The research team reports an increasing number of MRSA infections in humans, whether or not the affected people have had contact with infected pigs.
“The historically high use of antibiotics could have led to the development of this highly antibiotic-resistant strain of MRSA in pig farms,” confirms study co-author Dr. Gemma Murray.
Extremely Stable Antibiotic Resistance in MRSA
"We have found that the antibiotic resistance of MRSA in farms is extremely stable - it has persisted for several decades and also during the spread of the bacterium to different species of livestock", underlines the scientist.
Reducing antibiotics cannot stop the spread of MRSA
Although the use of antibiotics in European livestock farming has fallen sharply in recent years, resistance to CC398 being very stable, the drop has a limited impact on the spread of this strain of MRSA.
Spectacular spread of MRSA in ten years
The CC398 strain is now found in a variety of livestock, but most commonly in pigs. According to the research team, the increase is particularly dramatic in pig farms in Denmark.
In 2008, less than five percent of herds were positive for CC398 in Danish pig farms. In 2018, this percentage increased to 90%. The bacteria can spread unnoticed among pigs because they do not cause disease in animals.
In humans, however, MRSA can cause serious infectious disease, in part because bacteria of the CC398 strain are able to evade the human immune system.
"Understanding the presence of CC398 in European livestock - and its ability to infect humans - is key to addressing the risk it poses to public health," said the study's lead author, Dr. Lucy Weinert emerges.
The evolutionary history of MRSA is examined
As part of the study, the team pieced together the evolutionary history of certain genetic elements of MRSA that made the bacteria resistant to antibiotics and this resistance remained stable for decades.
According to the researchers, another genetic element called φSa3 ensures that CC398 can evade the human immune system. However, this element has fluctuated in recent years, suggesting that the bacterium can adapt quickly to human hosts.
“While human MRSA cases associated with farm animals represent only a small fraction of all MRSA cases in the human population, the fact that they are increasing is a worrying sign,” Weinert concludes. (vb)
Author and source informationShow now
This text corresponds to the specifications of the specialized medical literature, medical guidelines and current studies and has been verified by health professionals.
Graduate editor (FH) Volker Blasek
Sources:Gemma Murray, Xiaoliang Ba, Lucy A Weinert, et al. : Stable antibiotic resistance and rapid human adaptation in livestock-associated MRSA; in: eLife (2022), elifesciences.orgUniversity of Cambridge: A highly antibiotic-resistant strain of MRSA that emerged in pigs may jump to humans (published: 28.06.2022), cam.ac.ukFederal Center for Health Education: profile of the MRSA pathogen (as of: April 24, 2018), infection protection.de
This article contains general advice only and should not be used for self-diagnosis or treatment. It cannot substitute a visit to the doctor.