Team finds new antibiotic resistance gene in Salmonella from broiler chickens

May 22, 2017, American Society for Microbiology
Salmonella forms a biofilm. Credit: CDC

A team of investigators from Agriculture and Agri-Food Canada, Guelph, Ontario, has discovered a gene that confers resistance to the important broad-spectrum antibiotic, fosfomycin. The researchers found the gene in isolates of the pathogen, Salmonella enterica, from broiler chickens. The research is published in Antimicrobial Agents and Chemotherapy, a journal of the American Society for Microbiology.

The gene, dubbed fosA7, confers a high level of resistance to fosfomycin, which is otherwise a safe and effective agent for eliminating infections caused by multidrug resistant bacteria. (The "7" in fosA7 indicates that this is the seventh antibiotic resistant fosA gene that has been discovered.)

Currently, there is only limited fosfomycin resistance among Salmonella species, said corresponding author Moussa S. Diarra, PhD, Research Scientist in Food Safety at Agriculture and Agri-Food Canada. But the powerful resistance the fosA7 gene confers is worrisome, said Diarra. It could spread among different Salmonella serovars (a serovar is a strain of a species), as well as other bacterial pathogen species, via , due to increased use of fosfomycin in both clinical and veterinary settings, said Diarra. Thus, "vigilant monitoring for the spread of fosfomycin resistance in bacteria, isolated from humans and animals, is needed."

With that in mind, the researchers tested the strength of the resistance the gene could confer on the closely related Salmonella enterica serovar Enteritidis. To do so, they cloned the gene, and inserted it into the chromosome of non-antibiotic resistant S. Enteriditis. Their worries were confirmed: the gene boosted the minimum concentration of fosfomycin required to inhibit reproduction in the microbe by more than 256-fold.

These results provided strong support for the hypothesis that fosA7 is, indeed, responsible for fosfomycin resistance, and that if fosA7 were transferred to plasmids—renegade pieces of DNA that can insert themselves into different bacteria—it could induce a high level of resistance in the recipient bacterial strain, according to the report.

The product of the fosA7 gene is an enzyme called glutathione-S-transferase. It inactivates fosfomycin by binding to it, and rupturing a molecular ring structure which is part of the antibiotic.

Fosfomycin resistance are often present in multidrug resistant bacteria. "This could further challenge the use of fosfomycin as an alternative treatment approach against urinary tract infections caused by both multidrug resistant E. coli, and blood infections from multidrug resistant Salmonella," said Diarra. So far, the investigators have found fosA7 only on S. enterica serovar Heidelberg and three other serovars of this species. A serovar is a strain of a species.

Salmonella enterica serovar Heidelberg—the strain in which the researchers found fosA7—is among the most common causes of human salmonellosis worldwide. The rise of resistance to multiple antibiotics, particularly to extended spectrum cephalosporins in Heidelberg has limited the number of therapeutic options against this Salmonella serovar. In the current study, the investigators found this gene in all of 15 Salmonella Heidelberg isolates in their collection.

The American Society for Microbiology is the largest single life science society, composed of over 50,000 scientists and health professionals. ASM's mission is to promote and advance the microbial sciences.

ASM advances the microbial sciences through conferences, publications, certifications and educational opportunities. It enhances laboratory capacity around the globe through training and resources. It provides a network for scientists in academia, industry and clinical settings. Additionally, ASM promotes a deeper understanding of the microbial sciences to diverse audiences.

Explore further: Researchers discover new variant on notorious resistance gene

Related Stories

Researchers discover new variant on notorious resistance gene

March 6, 2017

Polymyxin antibiotics are used as a last resort to treat certain multidrug resistant bacteria. A team of investigators in China has discovered a new variant on a well-known gene that causes resistance to polymyxins and others. ...

Novel antibiotic resistance gene in milk

April 27, 2017

Researchers of the University of Bern have identified a new antibiotic resistance gene in bacteria from dairy cows. This gene confers resistance to all beta-lactam antibiotics including the last generation of cephalosporins ...

CDC: Drug-resistant foodborne bacteria on rise

June 10, 2015

(HealthDay)—Antibiotic-resistant infections from foodborne germs still cause about 440,000 illnesses in the United States each year, the U.S. Centers for Disease Control and Prevention reported Tuesday.

Recommended for you

Researchers measure gene activity in single cells

March 16, 2018

For biologists, a single cell is a world of its own: It can form a harmonious part of a tissue, or go rogue and take on a diseased state, like cancer. But biologists have long struggled to identify and track the many different ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.