Trial into mouthwash treatment for gonorrhoea expands

Listerine does kill gonorrhea bacteria.
Image: simarik via Getty Images

by Anne Crawford

The Melbourne Sexual Health Centre (MSHC) and Monash University’s Central Clinical School have expanded a trial to further investigate a finding made last year that use of a commercially available mouthwash could curb the rising rate of gonorrhoea.

Preliminary research published online in the journal Sexually Transmitted Infections in December found that a one-off rinsing and gargling Listerine could inhibit the growth of the bacteria responsible for pharyngeal gonorrhoea.

The news has been greeted with much interest ever since the MSHC Director, Professor Kit Fairley, spoke about the yet-to-be published findings at the British Association for Sexual Health and HIV (BASHH) in Oxford in July last year. A tweet Professor Fairley issued at the time similarly attracted attention around the world. The finding has been mentioned on dozens of online sites and media articles since publication.  

Dr Eric Chow, Senior Research Fellow at the MSHC, said that rising rates of the bacteria Neisseria gonorrhoeae among men who have sex with men (MSM), and declining condom use, make the need urgent for research into a preventive measure that doesn’t rely on condoms.

“The rate of gonorrhoea in Victoria is increasing year by year, and it seems a bit out of control,” Dr Chow said.

The increasing spread of the bacteria also heightened the risk of the emergence of antibiotic-resistant strains, he said.

The MSHC trial involved 196 gay/bisexual men who had previously tested positive for gonorrhoea in their mouths/throat, and who were returning for treatment at the clinic between May 2015 and February 2016. Of these, 33 men were randomly assigned to rinse and gargle with Listerine and 25 with a saline solution. The men using Listerine were 80 per cent less likely to test positive for gonorrhoea in their throat five minutes after gargling than were the men using the saline solution.

The finding though isn’t new. The manufacturer of Listerine claimed in 1879 – before the advent of antibiotics – that the mouthwash could be used to cure gonorrhoea but until now no published research has tested the claim. If effective, the mouthwash could become a cheap and easy way of helping to control the spread of the infection.  

However, the researchers caution that the trial had a short monitoring period, meaning it is possible the effects of the mouthwash might be short-lived. 

A larger, longer study funded by the NHMRC is currently underway to confirm the results. The OMEGA (Oral Mouthwash to Eradicate GonorrhoeA) Study ­is a double-blind trial and is expected to test 500 men across six clinical sites in Sydney and Melbourne. Laboratory work to test different brands of mouthwash to see if they have a similar effect to Listerine will also be undertaken.

Reference:

Chow EP, Howden BP, Walker S, Lee D, Bradshaw CS, Chen MY, Snow A, Cook S, Fehler G, Fairley CK. Antiseptic mouthwash against pharyngeal Neisseria gonorrhoeae: a randomised controlled trial and an in vitro study. Sex Transm Infect. 2016 Dec 20. pii: sextrans-2016-052753. doi: 10.1136/sextrans-2016-052753. [Epub ahead of print]

See also another article by MSHC authors on the transmission of gonorrhoea and the need for  interventions appropriate to this: 
Fairley CK, Hocking JS, Zhang L, Chow EP. Frequent Transmission of Gonorrhea in Men Who Have Sex with Men. Emerg Infect Dis. 2017 Jan;23(1):102-104. doi: 10.3201/eid2301.161205.