A dangerous, ‘silent reservoir’ for gonorrhea: The throat

The human throat houses billions of bacteria, most of them harmless. But one species is becoming more common, and it is anything but benign.

Drug-resistant gonorrhea has been on the rise for years; the World Health Organization has reported an increase in more than 50 countries. Now scientists say the epidemic is being driven by a particular mode of transmission: oral sex.

“The throat infections act as a silent reservoir,” said Emilie Alirol, the head of the sexually transmitted infections program at the Global Antibiotics Research and Development Partnership. “Transmission is very efficient from someone who has gonorrhea in their throat to their partner via oral sex.”

Oral gonorrhea is hard to detect and treat. Even more worrisome, these bacteria pick up resistance to antibiotics directly from other bacteria in the throat — and then are communicated to sex partners.

Only one commercially available antibiotic still consistently works against drug-resistant strains. And now there’s a new worry: so-called super gonorrhea, impervious to every standard treatment.

“This bug always outsmarts us,” said Dr. Jeanne Marrazzo, an infectious disease specialist at the University of Alabama at Birmingham. “It’s really good at figuring out ways to become resistant.”

Whenever the human body is exposed to antibiotics, the natural bacteria of the throat are exposed, too. Over time, they can build up resistance to the drugs.

That is not a concern until harmful bacteria are introduced. Sharing close quarters with the natural occupants of the throat, the invaders exchange DNA in a process called horizontal gene transfer.

This process relies on plasmids, small circular DNA molecules that contain the bacterium’s genetic material but are separate from chromosomes. Plasmids can easily be transferred from one bacterial species to another when close by.

When the plasmid in question contains drug-resistant genes, the gonorrheal bacteria acquiring it become resistant to antibiotics, too. Thirty percent of all new gonorrhea infections in the U.S. are resistant to at least one drug, according to the Centers for Disease Control and Prevention, and studies show that gene transfer is largely the reason.

“The worry is that if we don’t stop this, if we don’t treat it properly, we’re going to see this happening more and more,” said Dr. Michael Mullen, an infectious disease specialist at Mount Sinai Hospital in New York.

Worldwide, gonorrhea infects about 78 million people each year. The number has been rising in recent years, partly because of decreasing condom use as fear of HIV transmission has waned, and because of poor detection rates, failed treatments and increased travel as people carry drug-resistant strains from one country to another, according to the WHO.

Drug-resistant strains have increased in many countries in recent years, most notably in India, China, Indonesia, parts of South America, Canada and the United States.

Diagnosing oral gonorrhea typically involves taking a sample from the infected area and growing the bacteria in a lab. But swabs from the throat often do not yield enough bacteria. Even when detected, oral infections are harder to treat. Antibiotics are delivered in the bloodstream, but there are fewer blood vessels in the throat.

Untreated throat infections can spread to the genitals, where they can cause testicular and pelvic pain in men, and can be particularly dangerous for women, causing pelvic inflammatory disease, ectopic pregnancies and infertility.