Multi-drug resistant gonorrhoea and the promise of a vaccine
In the wake of news that ‘super-gonorrhoea’ has the potential to become a public health threat, researchers discover a potential roadmap to a vaccine.
Globally, approximately 78 million people contract gonorrhoea each year – and until now, no protective vaccine has come even close to being effective.
Just last week (July 7), the World Health Organization (WHO) released a statement warning of the rise of drug resistant gonorrhoea – meaning that there are now strains that are not only hard to treat, but some which even evade last resort antibiotics.
Gonorrhoea, caused by the bacteria Neisseria gonorrhoea, is a sexually transmitted infection that can infect the genitals, rectum and throat. It disproportionately affects women and, if left untreated, complications may result in ectopic pregnancy, pelvic inflammation and infertility. It also results in an increased risk of HIV.
Dr Teodora Wi, Medical Officer in Human Reproduction at the WHO said: "The bacteria that cause gonorrhoea are particularly smart. Every time we use a new class of antibiotics to treat the infection, the bacteria evolve to resist them."
Critically, many of the cases of drug resistant gonorrhoea have been detected in high-income countries, where surveillance is more advanced. But according to the WHO, the issue may well be more prevalent.
"These cases may just be the tip of the iceberg, since systems to diagnose and report untreatable infections are lacking in lower-income countries where gonorrhoea is actually more common," adds Dr Wi.
Drug and diagnostics development
There are currently very few new drugs in development to combat gonorrhoea. Mainly because it is not commercially beneficial for a pharmaceutical company to invest in antimicrobials, as they are only used for short periods of time and they can quickly become resistant.
Diagnosing gonorrhoea is also an issue. Unlike HIV testing, there are currently no affordable and point-of-care tests, meaning samples have to go to a lab. Doctors may prescribe antibiotics based on symptoms when it may not actually be gonorrhoea – resulting in inappropriate use of antibiotics.
“To control gonorrhoea, we need new tools and systems for better prevention, treatment, earlier diagnosis, and more complete tracking and reporting of new infections, antibiotic use, resistance and treatment failures,” said Dr Marc Sprenger, Director of Antimicrobial Resistance at WHO.
“Specifically, we need new antibiotics, as well as rapid, accurate, point-of-care diagnostic tests – ideally, ones that can predict which antibiotics will work on that particular infection – and longer term, a vaccine to prevent gonorrhoea.”
A potential vaccine
Just days after the release of the WHO statement, a study from New Zealand revealed a possible link between a meningitis vaccine and lower rates of gonorrhoea, which the authors state could inform the development of a potential vaccine for both gonorrhoea and meningococcal infections.
The research, published in the Lancet, discovered that among individuals given the outer membrane vesicle (OMV) meningococcal group B vaccine (MeNZB), gonorrhoea incidence decreased by around a third (31%) – even after accounting for confounding factors such as age, sex, geographic location and ethnicity.
In fact, it was only when individuals were co-infected with chlamydia, that the vaccine became less effective.
Around 1 million people under the age the age of 20 in New Zealand received the MeNZB vaccine from 2004-2006, during a mass immunization programme to combat an epidemic of meningitis B. After witnessing decreasing rates of gonorrhoea and constant rates of chlamydia – ruling out any changes in sexual behaviour over time – the researchers suspected that the antifungal vaccine had an effect on gonorrhoea specifically.
This is the first time any vaccine has had any protective effect against gonorrhoea. According to the authors:
“These findings provide experimental evidence that these vaccines could offer moderate cross-protection against a related organism, by an unknown mechanism of immunological protection.”
While the results are no doubt positive, the authors note that further research is needed to understand exactly how the vaccine provided protection. This will inform further development and may help eliminate the need for treatment using antibiotics.