MST résistante aux antibiotiques
WHO demands action on drug-resistant gonorrhoea
Staging a comeback (Image: CDC/Phanie/Rex Features)
Gonorrhoea, a sexually transmitted infection also known as "the clap", is making a comeback – and this time it may be incurable. New strains have emerged that resist the last few antibiotics that still worked against the disease.
In a rare public alert last week, the World Health Organization warned that highly resistant cases of gonorrhoea have now been detected in Japan, Europe and Australia. It is calling for a worldwide effort to track the superbug – and to develop new gonorrhoea drugs and vaccines.
That's a slim hope. Between the limited profits to be made from drugs that cure infections and the previous success of antibiotics against gonorrhoea, there has been little investment in the disease. "There are no new therapeutic drugs in development," says Manjula Lusti-Narasimhan of the WHO's Department of Reproductive Health and Research.
Yet epidemiological models show that the current official policies for managing gonorrhoea are virtually guaranteed to lead to a rebound in cases, and to antibiotic resistance.
Neisseria gonorrhoeae, also known as Gonococcus, infect an estimated 106 million people a year worldwide. The infection causes painful urination in men and can be symptomless in women, but left untreated it may cause painful pelvic inflammation and potentially fatal ectopic pregnancy. It can cause blindness in babies, and makes it easier to contract HIV.
It was among the first diseases to fall to antibiotics in the 1940s, but the bacteria readily acquire antibiotic resistance genes and keep them, even when the antibiotics they resist are no longer used. N. gonorrhoeae is now resistant to penicillin, and the subsequent families of antibiotics used to treat it.
Now only a couple of third-generation cephalosporin antibiotics are left. But resistance to these has been creeping up, and last year N. gonorrhoeae resistant enough to be dubbed a "superbug" was reported in Japan.
Most people clear the infection faster than they change sex partners, so don't spread the bug to someone new. But people who change partners faster, such as sex workers and promiscuous communities of men who have sex with men, are likely to pass on the infection. Targeting such groups for treatment caused gonorrhoea infection rates to drop steeply in industrialised countries since the 1970s – but now they are climbing again.
This could be because in models, treating these "core groups" is the only way to slash infection rates. But this is also an efficient way to select for antibiotic resistance, which then spreads widely. "It's a catch-22," says David Fisman of the University of Toronto, Canada.
Worse, the models show that relying on one drug until resistance builds up, then switching to another – precisely what health agencies have done – causes resistance fastest.
One way out might be diagnostic tests that reveal not just the strain of gonorrhoea responsible for infection, but which antibiotics it resists. Current DNA-based tests do not, meaning resistant infections are treated blindly, often with a drug that has no effect and can just worsen resistance. Fisman thinks this could be why gonorrhoea is increasing in some places.
The ultimate answer would be a gonorrhoea vaccine. Some efforts are underway, but have been unsuccessful – partly because the ancient disease is so well adapted to humans, people do not become immune even from repeated infections.
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