(Reuters Health) - Deep kissing with tongue may be a way that gonorrhea is passed on, even if romantic partners haven’t been otherwise sexually active, according to research from Australia.

Although the study involved only gay and bisexual men, the risk of transmitting gonorrhea orally is likely also present for heterosexuals and particularly sex workers, the study authors write in the journal Sexually Transmitted Infections.

“It’s important to understand that safe sex isn’t a catch-all for gonorrhea, which challenges previous sexual health practices,” said lead study author Eric Chow of the Melbourne Sexual Health Centre and Monash University.

Public health messaging has focused on condom use because most gonorrhea is thought to be transmitted during penile-anal sex among men who have sex with men. However, recent studies have suggested that sex accounts for only part of the documented cases, especially when gonorrhea occurs in the throat.

“Kissing may be riskier than previously thought,” Chow told Reuters Health by email. “This may help people understand how the infection was introduced, particularly if they haven’t been sexually active.”

Chow and colleagues surveyed 3,677 men who have sex with men between March 2016 and February 2017 at the Melbourne Sexual Health Center, which offers free walk-in service. The survey asked about the number of male partners during the past three months in three separate categories: kissing-only, sex-only and kissing-with-sex.

All of the men were tested for sexually transmitted diseases, and 229 men, about six percent, had throat gonorrhea infections. About six percent had anorectal gonorrhea and three percent had urethral gonorrhea. At an average age of 30, almost all of the men had kissing-with-sex partners in the past three months, and 70 percent had kissing-only partners, but just 38 percent had sex-only partners. Less than a third of the men reported having all three types of partner, but most had at least two of the types.

On average, the men had 4.3 kissing-only partners in the previous three months, as well as 1.4 sex-only partners and 5 kissing-with-sex partners. Kissing-only and kissing-with-sex were associated with throat gonorrhea but sex-only was not.

The odds of having throat gonorrhea nearly doubled for those with four or more kissing-only or kissing-with-sex partners. In addition, younger men had greater odds of having throat gonorrhea, which was associated with younger men having more kissing-only partners, the study team notes.

“Gonorrhea rates continue to increase, and although some interventions are bending the curve of the epidemic, we need to continue to encourage screening,” said Dr. Lindley Barbee of the University of Washington in Seattle, who wasn’t involved in the study.

Future studies should investigate the different types of sex that may be related to gonorrhea transmission as well, she added, such as anal or oral sex. In addition, researchers should investigate specific kissing behaviors, including the duration, number of times or number of female partners kissed by bisexual men.

“This can be tough to study because people are not isolated and do all of these behaviors in the same setting,” Barbee told Reuters Health by email. “It’s hard to tease out which encounter or sexual behavior transmitted the infection.”

Chow and colleagues are now conducting a clinical trial that tests whether daily mouthwash use could reduce the risk of infection with the gonorrhea bacteria.

“We know it’s unlikely that people will stop kissing,” Chow said. “If this works, it could be a simple and cheap intervention for everyone.”

In the meantime, Barbee recommends remaining aware and getting tested. Throat gonorrhea can often be asymptomatic but may build resistance to antibiotics, which can make the gonorrhea itself tough to treat and potentially lead to more severe throat infections later.

“Gonococcus is able to scavenge DNA from other bacteria and interchange genetic material that can lead to antimicrobial resistance,” she added. “It’s important to understand what’s going on in our throats and treat it.”

SOURCE: bit.ly/2VF4WLr Sexually Transmitted Infections, online May 9, 2019.