Background Gonorrhoea is increasing among men who have sex with men (MSM). We aimed to determine whether Listerine, a commercial mouthwash product, has an inhibitory effect against Neisseria gonorrhoeae in a randomised controlled trial (RCT) and an in vitro study, and therefore may be a potentially useful agent for gonorrhoea control.
Methods In vitro: a suspension of ∼108 colony forming units per mL (CFU/mL) of N. gonorrhoeae was added to a serial of dilutions (up to 1:32) of alcohol-containing Listerine mouthwashes (Cool Mint and Total Care) for 1 min. A 10 µL aliquot was spread over the surface of a gonococcal agar plate and the number of N. gonorrhoeae colonies present at each dilution was calculated. The phosphate buffered saline (PBS) was used as a control. RCT: we recruited MSM with pharyngeal gonorrhoea who returned for treatment at the Melbourne Sexual Health Centre between May 2015 and February 2016. Untreated men were randomised to rinse and gargle either Listerine Cool Mint or saline for 1 min. Pharyngeal swabs were taken before and after rinsing and gargling for culture of N. gonorrhoeae. The analysis included only men who were culture positive for N. gonorrhoeae before using the allocated solution on the day of recruitment.
Results In vitro: Listerine mouthwashes at dilutions of up to 1:4 for 1 min resulted in significant reduction of total N. gonorrhoeae counts but PBS has no inhibitory effect against N. gonorrhoeae. RCT: a total of 196 MSM were recruited, 58 (30%) were culture positive before using the solution. After gargling the allocated solution, men in the Listerine group were significantly less likely to be culture positive on the pharyngeal surface (52%) compared with men in the saline group (84%) (p=0.013).
Conclusions This data suggest Listerine, significantly reduces the amount of N. gonorrhoeae on the pharyngeal surface. With daily use it may increase gonococcal clearance and have important implications for prevention strategies.
Trial registration number ACTRN12615000716561.
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Handling editor Jackie A Cassell
Contributors CKF conceived the idea that Listerine may be used as an alternative intervention to reduce the risk of pharyngeal gonorrhoea. EPFC, CKF, SW and DL contributed to the conception and design of the randomisation controlled trial. EPFC, BPH, GF and CKF contributed to the design of the in vitro laboratory study. EPFC, SW and DL involved in data management of the randomisation controlled trial. BPH involved in the laboratory testing, data analysis and interpretation of the in vitro laboratory study. EPFC involved in data analysis and interpretation of the randomisation controlled trial. CKF, MYC and CSB assisted with the data interpretation of the randomisation controlled trial. DL, AS and SC involved in study recruitment and acquisition of data. BPH provided the overall supervision of the in vitro laboratory study, and CKF provided the overall supervision of the randomisation controlled trial. EPFC wrote the first draft of the manuscript. All authors involved in revising the manuscript critically for important intellectual content and approved the final version.
Funding This work was supported by the Australian National Health and Medical Research Council (NHMRC) programme grant (grant number 568971). EPFC is supported by the Early Career Fellowships from the Australian NHMRC (number 1091226).
Competing interests None declared.
Patient consent Obtained.
Ethics approval Ethical approval was obtained from the Alfred Hospital Ethics Committee (number 544/14).
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement The corresponding author had full access to all the data in the study and had final responsibility for the decision to submit for publication.
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