Health officials in the US have identified a cluster of gonorrhea infections that exhibited unusual resistance against the last two main antibiotics known to work against the dreaded sexually transmitted disease.

Health officials reported the findings today at the 2016 STD Prevention Conference in Atlanta. It’s yet another disturbing reminder that our antibiotics are increasingly losing their effectiveness.

The unusually resilient cluster of gonorrhea infections, which were discovered in Hawaii, exhibited decreased susceptibility to ceftriaxone and a very high-level resistance to azithromycin—both of which are used as frontline drugs (i.e. the first and often most effective drug of choice for a given treatment). Together, these two antibiotics make up the dual regimen that’s the last available effective gonorrhea treatment option.

Neisseria gonorrhoeae, the bacteria responsible for gonorrhea. (Image: National Institute of Biomedical Imaging and Bioengineering)

Earlier this year, health officials sounded the alarm when they discovered a strain of gonorrhea that had developed resistance to azithromycin, but not ceftriaxone. The Centers for Disease Control and Prevention says this new cluster is the first in US to show such dramatically reduced susceptibility to both frontline drugs.

“Our last line of defense against gonorrhea is weakening,” noted Jonathan Mermin, a director at the US Centers for Disease Control and Prevention, in a statement. “If resistance continues to increase and spread, current treatment will ultimately fail and 800,000 Americans a year will be at risk for untreatable gonorrhea.”

This common sexually transmitted disease is caused by the Neisseria gonorrhoeae bacterium, and it infects both men and women. Symptoms of gonorrhea include a greenish yellow or whitish discharge from the penis and vagina, burning while urinating, swollen glands in the throat (due to oral sex), among others. If left untreated, it can cause serious health problems such as infertility, pelvic inflammatory diseases, and life-threatening ectopic pregnancy in women (when the fetus develops outside the uterus).

The highly resistant strain was isolated from seven individuals in Honolulu in April and May of 2016, and these infections all showed resistance to both azithromycin and ceftriaxone. All patients were treated successfully, but the level of resistance was disturbing.

“Hawaii is on the front line for antibiotic-resistant gonorrhea—we’ve been one of the first states to see declining effectiveness of each drug over the years,” noted Alan Katz, a public health official at the University of Hawaii. “That’s made us extremely vigilant, so we were able to catch this cluster early and treat everyone found who was linked to the cluster. But the future risk of gonorrhea becoming resistant to both of the recommended therapy medications in the United States is troubling.”

On a positive note, an experimental oral antibiotic, called ETX0914, is currently under development, but it could be years before it reaches clinical trails. And even if it does prove effective, it may only be a matter of time before it too becomes ineffective in the face of this ever-evolving bacterial infection.

[CDC]