Antibiotic resistance and bacterial sexually transmitted infections

Prevention in Focus PiF 2026 Spring

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Antibiotic resistance is an important consideration for the treatment and prevention of bacterial sexually transmitted infections (STIs). The spread of antibiotic-resistant STIs like gonorrhea and Mycoplasma genitalium (Mgen) makes these infections harder to cure and control, and there is a risk that the use of antibiotics for STI prevention will increase antibiotic resistance. The most effective way to limit the growth of antibiotic-resistant STIs is to limit overuse and misuse of antibiotics. Service providers can support clients by providing education on antibiotic resistance and explaining ways they can help limit its growth, while also supporting them to prevent and treat STIs.

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What is antibiotic resistance and why is it a problem?

Antibiotic resistance happens when a microorganism (usually bacteria) changes in ways that make it less vulnerable to a medication (antibiotic) used to treat it. As resistance develops, the antibiotic becomes less effective, and infections become harder to treat. Over time this can lead to antibiotics no longer working, making it easier for infections to progress and further damage a person’s health. 

Because antibiotic-resistant bacteria can survive treatment, the infection can remain in a person and be passed to others. This means that even people who have never taken an antibiotic can get an infection that is resistant to it. These antibiotic-resistant infections can then spread throughout communities, eventually becoming more common than non-resistant infections. 

The World Health Organization (WHO) identifies resistance to medications, including antibiotics, as one of 10 major global health and development threats.1 Antibiotic resistance is a leading cause of death worldwide.2 In Canada, rates of new infections caused by antibiotic-resistant microorganisms increased between 2018 and 2022.3 Several of these, including gonorrhea, are listed by the WHO as high priority.4 

How do human actions impact antibiotic resistance? 

As long as antibiotics are used, bacteria will develop resistance to them. However, overuse and misuse of antibiotics speed up the process. Overuse means prescribing or taking an antibiotic when it is not needed — such as prescribing an antibiotic when an infection is likely to clear safely on its own. Misuse means the drug is not taken or prescribed properly — for example, when a person does not finish taking all of the medication in a prescription, allowing the bacterial copies that are more resistant to survive, reproduce and get passed on. 

Concerning antibiotic-resistant STIs

Antibiotic resistance has been identified in several bacterial STIs. Two of the most concerning ones are gonorrhea and Mgen. These bacteria develop resistance easily and are already resistant to many antibiotics. Because few antibiotics are effective against them, these infections are challenging to treat, and the few effective antibiotics get used frequently, which contributes to increasing resistance to these antibiotics as well. 

Antibiotic-resistant gonorrhea

Gonorrhea is caused by bacteria called Neisseria gonorrhoeae. Untreated, it can lead to serious problems like chronic inflammation, infertility and arthritis.5 Gonorrhea is the second most common reportable bacterial STI in Canada, after chlamydia.6 Between 2010 and 2023, rates of new gonorrhea infections in Canada tripled from approximately 33 cases per 100,000 people to 105 cases per 100,000 people.7 

Gonorrhea easily develops resistance to new antibiotics. It has developed resistance to every type of antibiotic used for routine treatment8 including ceftriaxone, which is the last remaining first-line treatment for gonorrhea. Ceftriaxone-resistant gonorrhea has been identified in several countries, including Canada.9 This is very concerning because it increases the risk of untreatable gonorrhea infections. Gonorrhea is now classified by the WHO as an antibiotic-resistant high-priority infection, for which new treatments are urgently needed.4 

In 2021, 77.4% of gonorrhea test samples analyzed as part of Canada’s Enhanced Surveillance of Antimicrobial-Resistant Gonorrhea (ESAG) system showed resistance to one or more antibiotics. Antibiotic resistance was more common in samples from gay, bisexual and other men who have sex with men (gbMSM), at 85.2%.10 

Antibiotic-resistant Mgen (Mycoplasma genitalium)

Mgen is an emerging sexually transmitted infection caused by bacteria called Mycoplasma genitalium. Symptoms in women can include vaginal discharge or bleeding, discomfort when peeing and pelvic inflammatory disease (PID). In men, Mgen is linked to inflammation of the urethra (tube inside the penis). Global estimates of Mgen prevalence range from approximately 1% to 4% in the general population.11 In Canada, MGen is not a reportable infection, so there is limited information about how common it is.12 However, a 2017 study in Alberta found Mgen in 6.2% of STI screening samples from over 2,200 sexual health clinic attendees, suggesting that it is common.13 

Mgen is already completely resistant to many common antibiotics. As a result, only two types of antibiotics are currently recommended for treating Mgen in Canada: macrolides (such as azithromycin) and fluoroquinolones (such as moxifloxacin).12 However, resistance has emerged to these drugs as well: a recent global study estimated that 33.3% of Mgen-positive test samples were resistant to macrolides and that 13.3% were resistant to fluoroquinolones.14 Limited data from Canada suggest that resistance to these antibiotics may be even more common,13 particularly among certain populations, such as gbMSM.15 

Antibiotic resistance and doxyPEP 

Antibiotic resistance has received increased attention in the context of STIs lately because of growing awareness of a prevention tool called doxyPEP. DoxyPEP is the use of an antibiotic called doxycycline after sex to prevent bacterial STIs. Evidence now shows that doxyPEP is effective at preventing syphilis and chlamydia among gbMSM and trans women and partially effective at preventing gonorrhea.16–19 

On the basis of this evidence, a number of countries and organizations have produced clinical guidelines on doxyPEP use among gbMSM and trans women. This includes the Public Health Agency of Canada’s Recommendations on the use of prophylactic doxycycline for the prevention of bacterial STI.

Efforts to make doxyPEP more accessible have raised concerns that greater doxycycline use could increase resistance to doxycycline and similar antibiotics among both STI and non-STI bacteria.20 

Potential impact of doxyPEP on antibiotic resistance in STIs

In Canada, doxycycline is a first-line treatment for chlamydia and a second-line treatment for syphilis.21,22 No clinically significant doxycycline resistance has been documented in these bacteria so far. However, if this did happen, treating these infections would become more difficult.23 This would be a significant problem, considering the recent increase in these infections, and their potential to seriously damage health. Although doxycycline is not a first-line or second-line treatment for gonorrhea in Canada (because of high levels of resistance)6 it may still be useful in some circumstances. Extensive doxyPEP use could lead to doxycycline becoming completely ineffective against gonorrhea,24 further reducing the already-short list of treatment options for this STI.

Potential impact of doxyPEP on antibiotic resistance in non-STIs 

Doxycycline is used to treat not only STIs but many other bacterial infections as well. Increased exposure to doxycycline through doxyPEP could lead to increased resistance in these other bacteria, making these infections harder to treat. There is some evidence that the use of doxycycline and closely related antibiotics may increase antibiotic resistance in bacteria of the gums, digestive system and respiratory tract.25 More research is needed to adequately assess these effects.

Implications for service providers

Antibiotic resistance is an important problem for communities at risk of bacterial STIs to be aware of, because it can make some STIs harder to treat, and may need to be considered when making decisions about treatment and prevention. Clients who first hear about antibiotic resistance in the context of STIs may be misinformed, anxious or overwhelmed by this new consideration. Accurate and accessible information from a trusted service provider, can help to correct misconceptions, reduce anxiety and prepare clients to make informed decisions. 

Service providers can help by sharing information about antibiotic resistance, when appropriate, alongside other information about STI prevention, testing and treatment. Important messaging includes the following:

  • what antibiotic resistance is and why it is a concern
  • which antibiotic-resistant STIs are concerning and why
  • how overuse and misuse of antibiotics contributes to resistance
  • what is known and not known about doxyPEP’s possible impact on antibiotic resistance

Service providers can also help clients feel more empowered, by highlighting simple actions clients can take to limit the development of antibiotic resistance in themselves and their communities, such as: 

  • always taking prescriptions exactly as prescribed, including completing the full course, even after symptoms cease (this can be built into and reinforce existing messaging about the importance of adhering to medications) 
  • never using or sharing antibiotics from a previous prescription, prescribed to someone else or obtained from an unknown or unregulated source
  • raising any concerns or questions they may have about antibiotic resistance with their healthcare provider 

Related resources

Antimicrobial resistance and STIs: Should we be worried? – CATIE

Canada raises dose of preferred antibiotic for gonorrhea – CATIE News

Gonorrhea guide: Key information and resources – Public Health Agency of Canada

Mycoplasma Genitalium guide: Key information and resources – Public Health Agency of Canada

Recommendations on the use of prophylactic doxycycline for the prevention of bacterial STI (chlamydia, gonorrhea, syphilis) – Public Health Agency of Canada

CATIE statement on the use of doxyPEP to prevent syphilis 

References

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  2. Murray CJ, Ikuta KS, Sharara F et al. Global burden of bacterial antimicrobial resistance in 2019: a systematic analysis. The Lancet (London, England). 2022 Feb 12 [cited 2025 Sep 2];399(10325):629-55. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC8841637/
  3. Public Health Agency of Canada. Canadian Antimicrobial Resistance Surveillance System (CARSS): 2024 key findings. Available from: https://www.canada.ca/en/public-health/services/publications/drugs-health-products/canadian-antimicrobial-resistance-surveillance-system-2024-executive-summary.html
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  10. Public Health Agency of Canada (PHAC). Report on the enhanced surveillance of antimicrobial-resistant gonorrhea (ESAG): results from 2018 to 2021. 2024 [cited 2025 Sep 2]. Available from: https://www.canada.ca/content/dam/phac-aspc/documents/services/publications/diseases-conditions/enhanced-surveillance-antimicrobial-resistant-gonorrhea-esag-2018-2021/esag-report-results-from-2018-to-2021.pdf
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  15. Lê AS, Labbé AC, Fourmigue A et al. Mycoplasma genitalium infection among gay, bisexual and other men who have sex with men in Montréal, Canada. Canada Communicable Disease Report. 2023 Dec 22 [cited 2025 Sep 7];49(11-12):477-86. Available from: https://pubmed.ncbi.nlm.nih.gov/38504874/
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  25. Truong R, Tang V, Grennan T et al. A systematic review of the impacts of oral tetracycline class antibiotics on antimicrobial resistance in normal human flora. JAC-Antimicrobial Resistance. 2021 [cited 2024 Aug 25];4(1):dlac009. Available from: https://doi.org/10.1093/jacamr/dlac009

Externally reviewed by: Mandy Malone & Dr. Jessica Minion

About the author(s)

Dan Miller is CATIE’s knowledge specialist, HIV care and STI. He completed a master’s degree in public health at the University of Toronto and is an experienced health services researcher and communicator.