Almost half of men who have sex with men (MSM) with positive cultures for gonorrhoea from the pharnyx also had positive saliva samples, in a study from Australia, suggesting that saliva may act as a vehicle for transmission of the infection.

MSM who attended Melbourne Sexual Health Centre, between October 2014 and March 2015 were screened for pharyngeal gonorrhoea using a throat swab for cultures.

A total of 33 MSM with positive cultures were treated and on the day of treatment, two further throat swabs were taken, one for culture and a second for NAAT testing. A saliva sample was also requested for culture and NAAT testing.

Median age of the MSM recruited was 27 years. Of the 33 who tested positive on the throat culture at baseline, 61% (95% CI: 42-77%) had positive pharyngeal swabs, by culture, by day 7 and 42% (95% CI: 26-61%) had positive swabs by day 14.

Furthermore, 31 of the 33 men, 94% (95% CI: 80-99%) had positive swabs by NAAT by day 14. Only 18% (95% CI: 7-36%) had positive saliva samples by NAAT within 14 days.

Pharyngeal swabs were significantly more likely to be culture positive than saliva specimens. Out of the 14 men who were culture positive on the day of treatment, 6, 43%, (95% CI: 18-71%) also had positive saliva samples.

All 31 men who had NAAT positive pharynx samples also had positive saliva samples.

This study demonstrated that almost half of the patients with positive cultures for gonorrhoea from the throat also had positive saliva samples by culture.

The persistence of salivary gonorrhoea on culture and NAAT 14 days after the initial culture also suggests saliva contains viable culture-positive gonorrhoea so direct contact between penis and pharynx does not have to occur for gonorrhoea transmission to take place.

This also suggests saliva used for oral-anal sex would contain viable gonorrhoea.

Although only conducted on a small number of MSM in Australia, it seems for this sample at least, that saliva appears to be a plausible carrier of gonorrhoea infection in some people.

Another study, of 1,312 MSM, who attended the Melbourne Sexual Health Centre, suggests that using saliva as a lubricant for anal sex might be a risk factor for rectal gonorrhoea.¹

Rectal gonorrhoea was significantly associated with using the partner’s saliva as a lubricant for anal sex; odds ratio (OR) 2.48 (95% CI: 1.20-5.10). Rectal gonorrhoea was also strongly associated with pharyngeal gonorrhoea, adjusted OR 17.31 (95% CI: 6.29-47.63). 

The adjusted OR of having rectal gonorrhoea was 2.17 times higher among those who used their partner’s saliva as a lubricant compared with those who did not, after adjusting for age, condom use for receptive anal intercourse, pharyngeal gonorrhoea positivity and HIV status.

The population attributable fraction (PAF) of rectal gonorrhoea associated with using saliva for anal sex was 48.9% (95% CI: 7.9-71.7%). The adjusted PAF was 41.4% (95% CI: -4.1 to 67.0%) after adjusting for age, condom use for receptive anal intercourse, pharyngeal gonorrhoea positivity and HIV status.

Almost 40% of all gonorrhoea infections might have been prevented if men had not used their partner’s saliva for anal sex.

Dr Richard Ma

Chow EPF, Lee D, Tabrizi SN. Detection of Neisseria gonorrhoeae in the pharynx and saliva: implications for gonorrhoea transmission. Sex Transm Infect 2015;0:1–3. doi:10.1136/sextrans-2015-052399