Dutch scientists have discovered cases of MRSA infection with staphylococcus aureus in the families of pig farmers. It is clear, according to the results of their research, that the dangerous bacteria can spread from pets to humans, writes Science magazine.
The first infection was discovered in 2004. In June 2004, Andreas Voss from RadboudUniversity Nijmegen Medical Center examined a six-month-old girl who was sent for surgery for a congenital heart defect, among others. the presence of Staphylococcus aureus (golden staphylococcus), which is a great risk for this type of surgery. Voss and his colleagues found not only S. aureus, but also its most resistant form called methicillin-resistant S. aureus (MRSA).
The MRSA bacterium is resistant to most antibiotics from the beta-lactam group, i.e. they destroy the bacterial cell wall. Doctors were amazed. Although MRSA is reaching epidemic proportions in developing countries, infections with this bacterium are rare in the Netherlands, thanks to a vigorous find and destroy policy that was applied in the country in the mid-90s to test the presence of this superbug in Dutch healthcare facilities where it has spread from time to time.
Currently, in the Netherlands, the greatest risk of contracting MRSA is staying in an infected foreign hospital. The child examined by Voss, however, did not go anywhere and, as he himself stated in a statement for Science, we could not find the source of the infection. There was only one clue – the parents were pig breeders.
After a few weeks, a second patient with MRSA infection came to the hospital – also a pig farmer, and then a third – a child of a veterinarian who worked only with pigs was a stroke of luck – said the scientist. We had three unexpected cases within a short period of time where there were connections to pigs, Voss noted.
As Science writes, pigs and other livestock often and usually in a harmless manner acquire S. aureus. With the exception of one case reported in the scientific literature, pigs and other farm animals have repeatedly been found to acquire MRSA, but there was no known case where a MRSA strain jumped from these animals to humans. If the fears of Dutch doctors prove to be true, the new strain has acquired this skill, thus opening a new path for a potentially dangerous superbug spread among humans.
At first, we were very concerned that it would be a big problem that could spread to the entire population, said Science Jan Kluytmans, microbiologist at VU University Medical Center in Amsterdam, previously hired by Voss to help with the research. In the months that followed, the livestock threat of MRSA played a role in a controversial report in a special CBS Evening News series discussing the implications of the widespread use of medically important antibiotics by the livestock sector.
Their use allows S. aureus and other bacteria to swap entire packages of resistance genes, potentially transmitting resistance to antibiotics like methicillin, which is never even used in agriculture. These threats fuel the introduction of restrictions on the long-debated use of antibiotics; this summer, the US Food and Drug Administration proposed to recall many of them. The industry objected, stating that the risk was negligible. Both sides are using the emergence of a new superbug to support their positions. – describes Science.
As the magazine notes, the biggest concerns about this strain have not materialized. As the researchers found in the work, the bacterium jumps from pigs to people. This causes serious illness – albeit rarely – among farmers and veterinarians working with pigs and other livestock, although most carry harmless microbes in the upper respiratory tract.
However, that doesn’t mean they’re ready for human-to-human transmission, which means the chances of embracing the entire community appear low. However, MRSA is ready to mix and swap genes with other bacteria, making them more virulent, easier to transfer, and more difficult to treat – and this emerging new strain may go that way.
Is there anything to worry about? Of course, says infectious disease specialist Vance Fowler of Duke University Medical Center in Durham, North Carolina, USA, in a statement for Science. MRSA first appeared in hospitals where medical procedures transfer bacteria to unprotected areas of the human body and to patients who are susceptible to infections. Until the 90s, this was a minor threat and most of the S. aureus strains were methicillin-sensitive. However, MRSA has replaced methicillin-sensitive strains and acquired resistance to other antibiotics, making hospitals truly unsafe.
Currently, S. aureus is responsible for 20 percent. cardiovascular infections, and 65 percent. S. aureus infections in intensive care units are resistant to methicillin in addition to other antibiotics.
MRSA killed 18,650 Americans in 2005, researchers from the US Centers for Disease Control and Prevention (CDC) reported in the 2007 issue of The Journal of the American Medical Association. This is a higher mortality rate than that associated with HIV / AIDS.
For years, hospitals have been associated with the most serious MRSA infections. Some strains began to circulate in a wider social setting, mostly between people in small spaces like marketplaces, prisons, and among vulnerable family members. These bacteria also appeared among people practicing contact sports – it was found in 2008. Since the 90s, the line between infections associated with hospitals and communities has started to blur. Strains previously limited to hospitals begin to infect healthy people, while the strains previously encountered in society infect many hospital patients.
Three isolates from the hospital in Nijmegen turned out to be one strain named ST398 by the researchers.
With the permission of the patient’s father, Voss’s team grew the bacteria from the pigs on his farm and tested him and 25 other farmer farmers. Two months after the girl was diagnosed with the bacteria, they found out that one in four was a carrier of MRSA, compared with 0,03 percent. in the entire Dutch population. Although preliminary, the analyzes provided strong evidence that the new bacterium was derived from pigs. To confirm this route of transmission, Science writes, Kluytmans and Voss carried out a case follow-up study in which they checked data on MRSA infections stored at the Dutch National Microbiology Center.
In 2007, according to their report in Emerging Infectious Diseases, ST398 carriers were twelve times more likely to be pig farmers than non-farmers, and all MRSA isolated from farmers belonged to the ST398 strain. Cattle breeders were 20 times more likely to carry the strain. The strain also appeared in chickens, horses, dogs and cats, but its potential risk to humans was poorly understood.
Also, biologist Robert Skov from the Statens Serum Institut in Copenhagen, Denmark, in his case study published in Emerging Infectious Diseases, showed that this strain may be associated with pig farming. How aggressive this strain is known is known, but some of the data still deserve attention.
Scientists also tested the readiness of the ST398 strain to spread to humans and found that it does not spread easily outside farms.
A team led by Wolfgang Witte, a microbiologist at the Robert Koch Institute in Wernigerode, Germany, conducted an experiment in schools in North Rhine-Westphalia, where intensive pig farming is taking place, to show that if this strain is spreading among healthy people, it should be visible among students. The team, according to a study published last year in PloS ONE, found that 250 out of 462 students tested positive for S. aureus, but only three of them were carriers of ST398 MRSA in the upper respiratory tract. They all lived on pig farms.
ST398 is also spreading to farms in North America, a recent study found. For example, in the last year, Tara Smith and her colleagues at Iowa State University in Ames reported on PloS ONE that nearly half of the pigs and 45 percent of the pigs. workers on pig farms in the US Midwest were carriers of ST398. However, this strain appears to be less dangerous in the US than in Europe – only one worker, according to Smith’s study, later fell ill.
As reported by a team led by biologist Michael Mulvey of the Canadian National Microbiology Laboratory in Winnipeg in a report in the April issue of Emerging Infectious Diseases, only 0,25 percent. of the 3,687 MRSA cases from the ST398 strain. Scientists speculate that this transatlantic difference may be due to the fact that ST398 emerged in Europe or in the US and Canada had greater competition from other MRSA strains that adapted to human existence. (PAP)