Researchers studying the C. difficile superbacterium say its antibiotic-resistant genes have been found in pigs and humans, meaning that not only is it possible to transmit bacteria on a larger scale, but also genes that resist the antibodies themselves. , may be able to spread through an animal vector to humans.
Clostridioides difficile, or C. difficile, is a bacterium that causes intestinal infection, causing symptoms such as diarrhea and inflammation of the colon, and is resistant to many antibiotics. Some strains have genes that allow them to cause extreme damage, and this can be life-threatening, especially in elderly patients who are receiving antibiotics for other problems.
It is also considered one of the most significant threats to antibiotic resistance in the world. In 2017, C. difficile caused more than 223,000 cases, 12,800 deaths and cost $ 1 billion in U.S. health care spending, according to the U.S. Centers for Disease Control and Prevention. A Canadian study found that between 2009 and 2015, more than 20,600 adults reported a C. difficile infection that developed in healthcare facilities.
“Our discovery of multiple and shared resistance genes shows that C. difficile is a reservoir of antimicrobial resistance genes that can be exchanged between animals and humans,” said Dr. Semeh Bejawi, a PhD student at the University of Copenhagen and one of the authors. of the study, said in a press release. “This alarming finding suggests that antibiotic resistance may be more widespread than previously thought, and confirms the links in the resistance chain leading from farm animals to humans.
C. difficile actually lives in the intestines of many people as part of the regular balance of the digestive system, but its growth is usually controlled by other bacteria.
The dangerous side of C. difficile can be unlocked by a common tool of the health system: antibiotics.
When a person takes antibiotics to deal with an infection, the medicine kills some of the other bacteria in the gut as well as the infection it is targeting – and because C. difficile is resistant to antibiotics if the balance of the gut system is discarded, C difficile can grow out of control and attack the lining of the gut. Recently, taking antibiotics is the biggest risk factor for developing inflammation or infection caused by C. difficile.
The researchers wanted to find out whether strains of C. difficile known to have antibiotic-resistant and toxin-producing genes are present in pigs and humans, which may indicate that zoonotic transmission helps. of C. difficile to develop into more dangerous forms and spread faster.
In a study presented this week at the European Congress of Clinical Microbiology and Infectious Diseases conference in Portugal, researchers looked at samples of C. difficile in 14 pig farms in Denmark and compared those samples with those from patients in a Danish hospital.
They examined stool samples from 514 pigs collected in 2020 and 2021 and found that 54 pigs had C. difficile. They then use genetic sequencing to isolate strains that have increased amounts of toxin-producing and drug-resistant genes. All samples from 54 pigs had genes that produce toxins.
The researchers compared the results of pigs with 934 isolates from people who were affected by C. difficile infection during this time.
Thirteen types of sequences matching pigs and patients in humans, such as the most common animal-related strain, ST11. In 16 cases, strain ST11 was identical in humans and animals.
Of the 54 pig samples, 38 had at least one antibiotic-resistant gene, and overall resistance was applied to a class of antibiotics commonly used to treat severe bacterial infections.
The researchers believe that this shows that the use of antibiotics in farm animals has the unintended side effect of producing more hypervirulent strains of C. difficile that could be transmitted to humans through zoonotic transmission.
“Excessive use of antibiotics in human medicine and as cheap production tools on farms is destroying our ability to treat bacterial infections,” Bejawi said.
Experts have noted the problem of overuse of antibiotics in farm animals and before – in August 2021 the UN issued a joint statement with the World Leaders Group on Antimicrobial Resistance, calling for a significant reduction in antimicrobials in food and farm animals, warned. that “the world is rapidly turning to a turning point where antimicrobials relied on to treat infections in humans, animals and plants will no longer be effective.
Bejawi added that researchers are concerned to find that some strains of C. difficile have many additional genes that are resistant to antibiotics that have no longer affected the bacterium.
“Of particular concern is the large reservoir of genes that confer resistance to aminoglycosides, a class of antibiotics to which C. difficile is inherently resistant – they are not necessary for resistance in this species. Therefore, C. difficile plays a role in the spread of these genes to other susceptible species, “she said.
“This study provides more evidence of the evolutionary pressures associated with the use of antimicrobials in livestock that select dangerously resistant human pathogens. This underlines the importance of adopting a more comprehensive approach to the management of C. difficile infection in order to consider all possible routes of transmission. “
One of the great limitations of the study is that although scientists have found similar strains of this bacterium in both pigs and humans, they have not been able to determine the direction of potential transmission – ie. whether this bacterium can jump from animals to humans, humans to animals, or both.
“The fact that some of the strains in both human and animal isolates are identical suggests that they could be shared between groups, but until we perform more in-depth phylogenetic analyzes, we cannot determine the direction of transmission that it can also be two-way, with bacteria constantly exchanging and expanding in the community and farms, ”Bejawi said.
Add Comment