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Antibiotic-resistant pathogen on the rise in Canada

For many, the fourteenth day of February is a day to celebrate love and romance – St. Valentine’s Day.

For the Public Health Agency of Canada, 14 February is Sexual and Reproductive Health Day – an annual awareness campaign to encourage Canadians to consider all aspects of their health, particularly their sexual health. The Agency encourages awareness of the risks involved with various sexual activities and the preventative strategies available, including regular screening.

Still, scientists at the Research Institute of St. Joe’s – Hamilton are expressing concern over the rising prevalence of an emerging sexually transmitted infection (STI). This new pathogen is called Mycoplasma genitalium, or M. gen. First isolated in humans in 1981, it was officially recognized as a new bacterial species in 1983. Unfortunately, commercial and lab derived tests have not been adequately evaluated for performance, which is necessary to gain approval by Health Canada for widespread use.

Since its discovery, M. gen has become notorious for its resistance to antibiotics, including azithromycin, particularly as its prevalence in the general population has increased. M. gen causes similar symptoms to chlamydia and gonorrheal infections, which includes acute or persistent urethritis in men. In women, M. gen has been associated with cervicitis, pelvic pain, urethritis, endometritis, salpingitis (inflammation of the fallopian tubes), and pre-term birth.

Although a 2016 study from Toronto reported infection rates of 4.5% in men and 3.2% in women attending a sexual health clinic, infection rates across Canada were unknown until a 2017 study was conducted by St. Joe’s researcher, Dr. Max Chernesky. The study, published in the journal Sexually Transmitted Diseases, used a “research use only” M. gen test on female samples from six Canadian provinces. (Other provinces were using STI testing methods that were incompatible with this study).

From that study, Chernesky’s lab found that roughly 13% of women with a chlamydia infection also tested positive for M. gen and 5% of chlamydia-negative samples were positive for M. gen. Furthermore, 47% of the confirmed positive tests were found to have mutations that lead to antibiotic resistance.

“We knew that Mycoplasma genitalium was in the general population, but this study was the first time we were able to determine the magnitude of M. gen presence and its resistance to commonly used antibiotics,” said Dr. Chernesky. “It was higher than most of us expected.”

Dr. Max Chernesky and Dan Jang in the microbiology research laboratory at St. Joseph's Healthcare Hamilton.

As a relatively new STI, not much is known about M. gen compared to other pathogens, such as chlamydia, gonorrhea, and HPV. However, researchers including Dr. Chernesky and his team are focusing their efforts on filling the knowledge gap.

Currently, the Chernesky lab is investigating 3 novel assays [molecular tests] for detecting and identifying antibiotic resistance from clinical samples. The results from this study will be presented at the World STI Congress in Vancouver in July, 2019. Data from this study may be used to help secure Health Canada approval.

“Several companies have new M. gen assays under investigation for Health Canada approval,” noted Chernesky, who further explained that “research use only” tests for M. gen can be validated and used. However, testing accuracy for any STI is important, in order to curtail spread, complications, and avoid the psychological impact of false-positive lab results.

According to Dr. Ameeta Singh, clinical assays that can simultaneously test for M. gen presence and potential antibiotic resistance “are critical in light of the high baseline resistance to the antibiotics which have activity against this organism.” Singh is a Clinical Professor in the Division of Infectious Diseases at the University of Alberta, and chair of the Canadian STI Guidelines Expert Working Group. She added that determining antibiotic resistance would reduce the unnecessary use of antibiotics.

Dr. Singh also explained that data from a number of countries show rising rates of M. gen strains that are resistant to macrolides and fluoroquinolones – the former is first line treatment for M. gen (e.g. azithromycin) while the latter is the treatment reserved for macrolide-resistant strains.

In the absence of clinical trials and the increasing prevalence of azithromycin-resistant strains, widespread clinical testing is being limited to patients with persistent symptoms and who test negative for chlamydia and gonorrhea. This thought process is being challenged because of the considerable numbers of asymptomatic men and women with M. gen already resistant to antibiotics.

Dr. Singh stressed that the importance of M. gen as an STI “has now been highlighted by Canadian data documenting the high prevalence of this organism,” pointing to a guidance document she helped develop with Chernesky and others. Singh is hopeful that more widespread testing will become available within 1 to 2 years as awareness increases and new assays are approved.

For now, researchers are reminding Canadians to be regularly tested for STIs, and to use protective strategies for their sexual health. Learn more about STIs and prevention strategies at the Sexual Health Ontario website and the Canadian Guidelines on Sexually Transmitted Infections.

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