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"A gargle a day keeps gonorrhoea away" is an unlikely slogan, but researchers believe it could hold some truth.

Recent studies have shown people can carry the sexually transmitted infection in their throats for weeks or months without symptoms.

And they could spread it to others through unprotected oral sex.

So investigators are looking at whether regular mouthwash might help stop the silent spread and experts think it is an idea that is worth exploring.

The 'clap'

Gonorrhoea is a bacterium and it can live in secretions in the throat as well as the penis and vagina and is spread by oral, anal and vaginal sex.

The disease - which was common in the first half of the 1900s until the discovery of an effective antibiotic treatment - is seeing a resurgence.

Doctors are worried that the number of new cases have been rocketing in recent years. Latest figures from Public Health England show that between 2012 and 2015 gonorrhoea infections rose by 53%, from 26,880 to 41,193.

Medics are increasingly concerned that the infection may eventually become untreatable, following the emergence of "super-gonorrhoea" - a drug-resistant strain that can dodge the usual antibiotic used to treat it.

Super gonorrhoea

Public Health England recently detected an outbreak of azithromycin-resistant gonorrhoea in northern England.

Fortunately, the strain can still be treated with another antibiotic called ceftriaxone, but PHE says there's no room for complacency and it's monitoring the situation carefully.

If azithromycin becomes ineffective against gonorrhoea, there is no "second lock" to prevent or delay the emergence of ceftriaxone resistance and gonorrhoea may become untreatable, they warn.

Cases were first spotted in Leeds in November 2014.

It then spread to the West Midlands and the south of England, with five cases found in London.

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By April 2016, the total number of people identified with the infection had reached 34 and included heterosexual couples and men who have sex with men.

Condoms are the best way to stop gonorrhoea spreading, but some experts believe there may also be another opportunity - mouthwash.

Studies suggests the throat could be a breeding ground for hard-to-treat bacteria.

Gonorrhoea can persist here without symptoms and swap DNA with other throat microbes that already know how to dodge certain antibiotics.

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Prof Christopher Fairley from Monash University has been testing the mouthwash theory in 58 male volunteers.

All of the men had detectable levels of throat gonorrhoea at the start of the trial.

He asked half of them to gargle and swill for a minute with saltwater while he gave the others a branded antiseptic mouthwash, bought from a supermarket, to use instead.

He retested them five minutes later to see if the gargling had helped. It appeared to, reducing the detectable amount of bacteria significantly more than the saltwater rinse.

Prof Fairley says more studies are needed to check how long this effect might last and what protection it might offer.

He's now recruiting more volunteers to take part in a three-month trial to see what impact daily gargling might have on gonorrhoea throat carriage.

Dr Anatole Menon-Johansson is an expert in sexual health and clinical director for the charity Brook.

He says Prof Fairley "could well be on to something".

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"I heard his presentation at a medical conference and I was really impressed. It's obviously still only a hypothesis. There's lots more to do and explore. But it's interesting, and it's got everybody thinking.

"If you could use a mouthwash there's a chance at the population level that it might make a difference to infection rates."

Men visiting his sexual health clinic are offered pharyngeal testing for gonorrhoea.

If the test comes back positive, the clinic runs extra checks to see what treatments the bacteria will respond to and which ones are doomed to fail because of drug resistance.

"These organisms have been with us humans for thousands of years and will continue to be. The challenge is working out ways to control transmission and make sure we have drugs that can still treat it."

Dr Gwenda Hughes, Head of the Sexually Transmitted Infections (STIs) Section at Public Health England (PHE), said: "Gonorrhoea infection in the throat usually has no symptoms but both men and women can get it by having unprotected oral sex.

"The only protection is by using condoms when having sex with new or casual partners and it's important to have regular check-ups at a sexual health clinic. Sexually active gay, bisexual or other men who have sex with men should get tested for STI's at least every three months.

"PHE continues to monitor, and act on, the spread of antibiotic resistance and potential gonorrhoea treatment failures by investigating identified cases, sexual history and treatment to make sure they are managed promptly."

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Gonorrhoea